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  1. Sometimes questions are raised as to whether it's worth increasing insulation levels and often there seems to be confusion as to what the "ideal" level of insulation is, or even what a "good" or "reasonable" level of insulation might be. I'm not sure whether or not the non-linear impact of improving insulation, in terms of the effect on the heating requirement, and hence running cost during cold weather, is widely understood. I've heard comments like "it's not worth improving the insulation from 0.16 W/m2.K to 0.12 W/m2.K because it would be 30% more expensive and only reduce the heat loss by 25%". Most of the time this is incorrect, because homes have heat sources all year around, from the occupants, incidental heating from appliances, solar gain and even pets (a medium sized dog is probably a four-legged 40 - 50W heater). So, I thought a really simple example might help some gain a better understanding of this non-linearity, and illustrate better why some are so evangelical about trying to improve insulation levels (and reduce ventilation heat loss, too, but I'll get to that another time). Let's build a pretend house, that for simplicity has no doors or windows and is a rectangular single storey box with a flat roof. For simplicity we'll assume it's on raised piles, with an air space underneath, just so we can use the same insulation level on all six sides and to make the sums simple. All I'm doing here is making a comparison, so this is a valid way of illustrating this effect. In our rectangular box house we have an average of 100W of incidental heating, coming from things like internet kit, a PC, a cordless phone base station, a TV, a phone charger, a few lights and a handful of intermittently used kitchen appliances. This is a pretty low figure - I struggle to keep our house background load below about 200W, without any lights on. The box houses two adults, giving out around 80 - 100W each and a dog, so lets say there is 220 W of heating coming from the occupants. The box also has a heating system that can deliver whatever power is needed to maintain a temperature of 20 deg C inside, and its night time, so there's no solar heating of the walls. Outside it's 5 deg C, a chilly winters night. This rectangular box is 10m long x 10m wide x 2.5m high inside, so has a total wall, floor and roof area of 300m2 and an internal floor area of 100m2, so fairly average in size (a bit bigger than our current 3 bed bungalow). So, we have a temperature difference between the inside and outside of 15 deg C (20 deg C - 5 deg C), an internal surface area of 300m2 and a constant incidental heating level of 320 W (220 W from two adults and dog, 100 W from electrical appliances and lights). First, lets see how much heat we need to put into this box from the heating system, if we have U values for the walls, floor and roof of 0.2 W/m2.K (K is degrees Kelvin, the same units as degrees Centigrade when only temperature difference is being compared): The total heat loss power, in Watts, can be calculated from the U value, the area and the temperature difference, so for this first example we get 300m2 area x 15 deg C temperature difference x 0.2 W/m2.K U value = 900 W. There is 320 W of heat coming from the occupants etc, so the heating system would need to deliver 900 - 320 = 580 W in order to keep the house at 20 deg C under these conditions. If this were by direct electric heating, then the heating cost would be about £2.09 per 24 hours. Next, let's see how much heat we need to put into this box from the heating system, if we have U values for the walls, floor and roof of 0.1 W/m2.K , in other words, we've made the insulation twice as "good", so might think we've halved the heating cost: The total heat loss power is now 300m2 x 15 deg C temperature difference x 0.1 W/m2.K U value = 450 W. This is what we'd expect, double the insulation effectiveness and halve the heat loss. However, when we now take away the incidental heat gain from the occupants, etc, of 320 W, the heating system needs to deliver 450 - 320 = 130 W in order to keep the house at 20 deg C under these conditions. If this were by direct electric heating, then the cost would be about £0.47 per 24 hours. So, by doubling the insulation level we've decreased the heating cost by about 78%, not the 50% that might have been expected. This is a very simplistic example, but it does illustrate why doubling up in insulation can give a far greater benefit than might be expected. It also shows why, when you improve the level of insulation you can reduce the heating requirement down to such a low level that for a lot of the time you don't need any heating. In that last example, turning on a few extra lights could heat this imaginary box home to a comfortable temperature on a cold night, whereas with only half the insulation it needs something that delivers 446% more heat.
  2. Hello all, I stumbled on this forum as part of a search for information about SunAmp batteries. I’ve spent a bit of time reading other threads on the topic and this seems to be a friendly and helpful piece of the internet. I’m on a quest to reduce the CO2 generated by the 3-bed 1960s semi (approx 98 sq m) where I live with my partner (no kids). We’ve insulated the upstairs, added some loft insulation, upgraded the double glazing and last year, we installed 5700W of solar panels and a Tesla Powerwall 2. I’d estimate we generate around 5000kWh a year from the panels, and export around 3000kWh of that. We’ve got our grid electricity usage down to about 500kWh per year. The biggest element of this being our electric shower (the Powerwall can only ever supply 5kW of the 10kW load). Gas is used for heating and hot water via a 15 year old Worcester combi-boiler - which I’m guessing is nearing end of life. Our gas usage is fairly low, but I’m looking to reduce that next, from the current 5000kWh per year (more when we have a cold winter). I'm not planning on replacing the gas boiler, meaning we'd be 100% reliant on electricity for heating and hot water. We’re on a deemed solar export tariff, and I’m looking to use as much of the energy generated as possible. I’ve also recently begun the switch to Octopus energy to take advantage of their Agile tariff, so it might be possible to shift much of our current gas energy usage over to electricity - but what would be best for us? GSHP not an option here (small garden) ASHP may be, but I’m conscious of the effort and cost of installing Underfloor heating. Air to Air an option? Right now I’m thinking a SunAmp for the hot water, or could the Uniq 12 supply our heating and hot water? Maybe we could supplement that with and a couple of electric radiators in the lounge and bedroom to keep us warm on demand? I’m not sure if that would be what we need especially if we have a long cold winter like last year (I’m on the South Coast of England). I would be grateful for any thoughts from anyone who has done similar or knows more than I do about these things. With thanks, David.
  3. A new idea. In the the latest House-Planning-Help podcast (HPH280), John Bootland (the boss of the Passive House Trust) mentions putting a little radiator near the front door to give a feeling or warmth as you enter. Interesting idea; never heard it mentioned before. Here is the clip (24:35): And the podcast:
  4. I am a fan of flexibility, having options, and for simplicity. When I build my new house I plan to include the wiring and pipes for both an ASHP and gas boiler. To go with the ASHP, I will also include UFH piping in my reinforced concrete raft foundation. Installing all the options at the time of the build costs peanuts. But how about adding one more cheap option: from a capital cost perspective, the cheapest of all. When I pour my my raft foundation, why don't I also include some electrical heating wire too embedded deep within the concrete? From checking on eBay, the cost of loose heating wire seems to be about £150 for 2kW. £150 really is peanuts! And it beats even a Willis heater for simplicity. Wet UFH after all needs a manifold, a pump, regulators, etc. While I would still have all the other options available later, I could use the wire heating for the first couple of years while I learn how my new house responds. What does everyone think? Bad idea?
  5. Good evening everyone, My name is Vaughn and I live in Sussex. I've joined the group, both as an aspiring home builder (in the future), but also to offer advice, where I can. I specialise is heating controls (and employed by one of the world's largest heating controls manufacturers). I also ran my own plumbing and heating business in the South East for 9 years, installing gas, LPG, and biomass boilers, heat pumps, solar thermal and a little solar PV too. I have particular interest heating controls, and renewable energy sources for domestic properties. I am active on other social media platforms, mainly Facebook, Twitter and Instagram. I look forward to participating as and where I can, and learning as well as sharing knowledge within the community. Regards, Vaughn.
  6. Currently have a 300 litre UVC ready for a heat pump to handle hot water + heating at a later stage but in the meantime like several others on the forum I would like to add a Willis heater between the manifold flow/return to run our UFH system. System is 3 x 100m loops all to be run as one zone in a 100mm screed. Wunda manifold is installed minus a pump at this stage. Wiring wise 3 core + earth from the stat is in place and power can be added from the plant room board easily. I would like to finalise and order the necessary components so if someone could advise if I've missed anything it would be greatly appreciated... Wilo manifold Pump from Wunda + Isolators Digital room thermostat (recommendations?) Willis jacket + immersion Timing Switch to ensure E7 use Electricians will fit all wiring and controllers but I supply everything. Possibly a 2 port valve as per @Nickfromwales recommendation in this thread but not sure if this is necessary? Trying to keep it as simple as possible at this stage.
  7. Hi Folks Looking for some guidance before leaping into E bay. Have spotted a used Samsung 9KW ASHP complete with tank and buffer tank and all expansion tanks and controls etc. Following from the listing:- 250ltr Santon Premier Tank Plus Pre-Plumbed Unvented Mains Pressure Water Heater with wiring. 120ltr Gledhill SL Plus Multi Buffer EE Tank plus pump. Expansion Tanks. Samsung and Siemans Controller Units including wall mounted controller and room stat. Fernox TF1 Total Filter Unit. All Instruction Manuals. However from the limited research I have done on the tanks, they do not seem optimized for ASHP IE larger coil, although I am not certain. Also what is the real world expected service life of the heat pump and compresser. I am planning on using it to run underfloor heating and also domestic hot water, planning on fitting a 3KW PV array. Currently have gas, so new ASHP kit + PV seems expensive/long payback time, however I like being less grid dependant, but need to buy secondhand to justify the costs. No plans to register for RHI. Here is the E bay link The 9KW seems about right when comparing the results from the excellent JS Harris heat loss spreadsheet, it is posibly larger than required, but seems they run better a little oversized. thanks
  8. Still at planning stage.... As we are on sloping site we are planning to have the living area on first floor and bedrooms beneath. I had it in my head that we would have a pot & beam floor as we are looking at UFH from ASHP. What about bedrooms? I have read elsewhere on here that upstairs bedrooms require little or no heat as heat comes up from heated rooms below. We won't have that. There will be a far amount of solar gain, in fact I am concerned about over heating, so will probably have MVHR system. Could this be utilised. Ideas please.
  9. Hi all, I am just completing a conversion but hired professionals for UFL. What I find strange is that the manifold (RED) is in the kitchen, and all sections (4 excluding kitchen) go through the kitchen floor and not through the staircase (behind the kitchen) and therefore leaving the potential to overheat the kitchen, when all areas are on and kitchen is already at temperature. Should't they have taken into consideration that the kitchen is potentially the warmest place in the house and it will become a potential sauna? Also the Manifold is right behind the oven and stove. Can I should I insulate the pipes from the screed? Will lay down normal sand+cement screed... Any pointers really appreciated. Thanks
  10. Been quite a bit if talk about thermostats and temp just recently and got me thinking what do people have their house temp set at? I used to do some work for a lady that had her house set at 27c and I used to perspire profusely. A young couple rent a house of us and they have it set at 25c. We have our house set at 19c and will prob be happy with 20/21 when we move into our new house.
  11. When I laid the wet UFH pipes in our concrete slab I put a loop in both bathrooms. Now I am hoping to put an electric mat under the tiles above the wet pipe system unless the collective say otherwise. Like some I am hoping to have a subtle background heat (electric)from the bathrooms to heat the house before we go full wet pipe but not sure if this is ok above the wet pipe system. TIA
  12. Of getting someone to commision a boiler/ufh system when it is already installed but not commissioned or pressure tested. So much for having plumbers I can rely on. They installed the boiler and ufh control last week. Everything was supposed to be finished by last Friday but unfortunately it wasn't. They left at 8pm last Friday with promises to come back today (Thursday) to complete. Couldn't get before then because of other promised work. Message at lunchtime today to say that they couldn't make it but 'should' be able to come next Thursday or Friday. The week after next, one is going away for the week (and the van is his). Absolutely fed up with this now. I should have been able to move in next week.
  13. Hi, I wonder if anyone can help please ? My In-Laws bought a bungalow a few years ago that had been fitted with a Kingspan Aeromax ASHP and have had problems with it ever since. Theres a whole list of stuff that’s been allegedly done, and by several people. The bottom line is that they get plenty of hot water, but when conditions are cold they don’t get any heating.........which is kind of when you need it ! We live an hour away and I’ve been letting them try to deal with this but I feel I need to step in as they are throwing good money after bad and no one they have around seems to truly know the system. Having read this forum there seem to be some very knowledgable & helpful people about. I notice that the Kingspan are, like a few others, just a rebadged version of a make called Carrier. I also notice from some extremely insightful posts from JSHarris that these units aren’t very well set up for the UK winter. Can anyone give any advice please ? If I need to buy one of these command units to reprogramme the system, assuming anyone knows the required parameters, then I’m happy to do that. For the record, I have no experience with these systems, or heating in general but I am a mechanical engineer with some electrical experience, so I should be able to do most stuff. Thanks for any help. Cheers, Lyndon
  14. In this entry I'm going to discuss in more detail how I came to choose our heating and hot water system, and how it has performed to date. As other forum members have found, deciding which fuel source and type of technology to use in a low energy house, is a challenge given the different requirements each of us has. We had three stipulations – low running costs, hot water available on tap 24/7 and maintenance of the whole house at an even and constant temperature 24/7. Having calculated our heating demand, taking the impact of solar gain, incidental household gain, human occupancy and wind speed into account, I was confident that I had a good indication of the amount of heating I would need. I was also confident, based on historical use, of the amount of hot water we as a family use. Living in an area without mains gas, my options were somewhat limited to using either oil or electricity as my fuel source. LPG was initially considered but discounted due to the lack of availability in my location. As part of the decision making process, I spent a fair amount of time carrying out a cost comparison of both oil and electricity based heating and hot water systems, using 500kWh increments from 2500kWh to 5000kWh. I considered direct electric of various type, oil and air source heat pumps, both air to water and air to air. Solar PV was also considered and costed in terms of each method of heat and hot water delivery. In line with previous cost comparisons that I had carried out, I found direct electric to be the most cost effective in terms of capital outlay and running costs when both heating and hot water demand were less than 2500 kilowatt hours each year. As heating requirement and hot water requirement increases so the balance began to tip in favour of other technologies. Oil was quickly dropped from the list as it became apparent that any rise in fuel prices over then then low point, would significantly increase running costs. Having conducted significant investigation in respect of the viability of Sunamp units, although attractive in many ways, I found that the capital outlay and running cost was simply too high to be able to justify, given that the main benefit (low heat losses) were not as critical for me as they have been for others. Part of that decision was also driven by the cost of fitting Solar PV, which in our remote location was extortionate. I looked into a non MCS DIY install, but couldn’t make the figures stack up, the break-even point being around 17 years. Much as I wanted to install PV, it didn't make any sense financially. In time, I hope to revisit PV, if and when battery storage reduces the break-even point to a more realistic timescale. A wind turbine, given our location and the virtually constant presence of wind, would have been an ideal energy source and paired with Sunamp technology, probably unbeatable. The proximity of nearby houses ruled out that option in terms of planning permission. Air to Air heat pumps were ruled out based on my own experience of them and a road test at a friends house. Neither myself or my good lady found them particularly pleasant as a heat source. Having gone through the list of options, an air to water air source heat pump, paired with a large UVC and UFH for the distribution of heat, represented the best balance in terms of capital outlay, running costs and crucially, comfort and convenience. We opted for a package from Mitsubishi Ecodan, an 8.5kW heat pump and 300 litre pre-plumbed cylinder fitted with the Mitsubishi FTC5 control panel. Given our location, we opted for the coastal model, which is treated with acrylic resin for enhanced corrosion resistance. Whilst a pre-plumbed cylinder is more expensive than a bare cylinder and associated parts, after taking labour (plumber and electrician) into account, I found there was very little difference in cost. I sourced the package from a trade supplier, Secon Solar. I found their price list while searching online and having phoned the company, and perhaps fortuitously speaking to the managing director of the firm, found they were quite happy to sell me package at trade / installer price, the bonus being that delivery to my location was free. The package is configured for the UK market, the only difference to the system as sold in the rest of Europe (AFAIK) being that the cooling function of the heat pump is disabled so that the product complies with MCS approval for claiming RHI. It is however a simple task to activate the cooling function, by flipping a dip switch in the control module on the cylinder. Cooling can then be controlled from the master controller. As stated in an earlier blog entry, the heat pump and cylinder were fitted very quickly with simple connections on the plumbing side – flow and return from the ASHP, cold water, hot water and flow and return to the underfloor heating manifold. Electrical connections consisted of power to the ASHP, a cable from the ASHP to the control module and a plug-in controller. I had initially planned to have the cylinder in the utility room close to the ASHP Monobloc, but changed the location to a service cupboard in the middle of the house, to reduce internal DHW pipe runs. This does mean a 15 metre pipe run for flow and return to the ASHP, but as virtually all is within the insulated envelope, it doesn’t represent much of an issue, and does not appear to be having an adverse effect on performance. The ASHP Monobloc itself is located beside our back door, open to the elements. It seems happy enough where it is, despite the wind that traverses the space between house and garage walls. Locating the ASHP within the garage itself was an option but one I decided against simply on the grounds that I didn’t want to give up floor space within the garage. A timber housing for the ASHP is something we may look at in the future. We opted to fit individual room thermostats to all 3 bedrooms, to give us the option of being able to reduce the bedroom temperatures if we so wished. We have not used these and keep the whole house at one temperature 24/7, treating the underfloor heating as a single zone. At present I only have limited data as to how the heat pump has performed since moving in. On board energy metering (energy consumed and energy produced) shows the CoP for heating has ranged between 3.5 and 4. DHW is maintained at 47C-50C in the cylinder, boosted every fortnight to 60 degrees by the immersion on an anti-legionella cycle. To date the CoP for DHW is 2.4 As members know, heat pumps are best suited to the production of low temperature heat as opposed to the higher temperatures required for domestic hot water. Whilst the CoP for DHW is lower than that for heating, the cost per kWh of our DHW, based on a CoP of 2.4, is 5p, which is significantly better than an E7 electricity tariff. We may be taking a hit on efficiency, but in reality all of the other options would have cost us more. The 300 litre capacity of the cylinder means that we have plenty of hot water on tap and can comfortably run a full bath and still have sufficient left over for another person to shower. The ASHP is currently operating on a 24/7 basis, providing heat input to the UFH and topping off the DHW as and when it determines it needs to, at whatever flow temperature it determines. Whilst that does sound like a recipe for high bills and high flow temperatures, in practice, the heat pump delivers the lowest flow temp it can get away with to maintain our set temperature. If I so choose, the controller lets me set various parameters such as heating curves or set flow temperatures, or indeed a timed schedule for heating and DHW. However,as the system is operating efficiently on its auto setting, and providing the level of comfort we want, I see very little reason to mess around and create my own settings. If say electricity tariffs were to change from a single tariff to a dynamic tariff, then I would have the option of timing the heat pump operation to coincide with lower rate tariffs. After much thought, and indeed discussion on this forum, I opted for an 8.5 kWh ASHP over a 5 kWh ASHP, as I felt happier running a larger unit more gently than pushing a smaller capacity unit harder. A 5 kWh unit would probably have sufficed, and in time, may be what the current unit is replaced with when it reaches the end of its life. We haven’t yet had to activate the cooling function as any overheating (defined as internal temperatures over 23C) caused by solar gain, can, as modeled, be managed by natural cross ventilation. Neither have we found it necessary to constantly circulate the UFH to even out the house temperature / redistribute solar gain from one part of the house to the other. In the heating season, we found that there was sufficient circulation of the UFH during the heating cycle to maintain the house at an even temperature. Outwith the heating season, when solar gain is at its peak, the house zones itself, the bedroom section remaining slightly cooler than the public areas, very useful on a warm summers day. Overall I’m very happy and impressed with our system. It has, so far, delivered everything we have asked of it in terms of comfort and convenience, and the running costs are low. I have the capability to cool the house (via slab cooling) if I so wish, and the option to bolt on a second zone pack onto the pre-plumb cylinder if I ever found it necessary to install a second heating / cooling function – i.e. fan coil or duct heater / cooler. The one criticism that I have is about the controller thermostat function and its hysteresis - 1C increments only. A finer degree of control would have been preferable. Our installation was recently inspected by an MCS accreditor (our plumber is going through the accreditation process). In due course that will give us the option to apply for RHI, although that will be very much dependant on whether the figures stack up.
  15. .....I thought to myself, as I instructed my man to cut the excess tail off a coil of Wunda UFH pipe. He cut some more, the noise got much worse. What’s going on ?!? We hadn’t hooked it up yet so a leak was impossible.......and then I twigged. The good folk at Wunda now sell the coils of UFH pipe pressurised with compressed air, and when I say pressurised, I mean pressurised. If you cut straight through you’d better be holding both pieces as it’s like stabbing a car tire ( probably ). They must have it close to 6 or more bar guessing by just how much air came out of a 100m coil. I then noticed the pipe ends. They’ve basically got plastic plugs glued / crimped into each end to keep the pressure up and keep any crud out, and I assume this pre-pressurising benefits in a couple of ways. Wunda know the pipe is sound at dispatch, you know it’s sound when you get it, and if dopy gits with long screws or multi tools inadvertently damage the pipe after installation / floors down etc there will be an undeniable “whoosh” of compressed air to let them know. Can’t help thinking that would also be of benefit during Ufh at the slab stage too as the pipe is likely to be a bit less susceptible to compression perhaps. Folly, or first class. ?
  16. I met with the Architect last week and ran into a problem. I've always been keen on using SunAmp with Solar PV as my preferred heating/hot water platform. I'm building a small 108m2 house so it's a good fit in my opinion. However....Building Control legislation has changed in recent years and I've to "opt in" to keep the bank happy. This means hands off first fix basically including MVHR that I was looking forward to installing. Anyway, that aside there's no registered installers in ROI for SunAmp and therefore no one can sign off such a system. Andy in SunAmp has been very clear on this point and even with the Amazing Nick willing to design and provide support I doubt any builder here will accept this risk and one I've just spoken to voiced his concerns. I've to go out to tender soon and don't want this to blow up on me! There are two likely heating options in my house at the minute: ASHP with underfloor, towel rails etc and hot water tank etc, no solar PV Solar PV and SunAmp UniQ to do the same without the hot water tank My plan was to live with SunAmp for a year and get an ASHP later if required. The more likely scenario is I get an ASHP and add SunAmp later (!) and possibly end up not using the ASHP afterwards! Well, I'll use it to recharge the SunAmp (ideally with a high temp ASHP unit) but it's the additional combined cost that I'd rather not spend. And retrofitting a SunAmp after a commissioned system is built and signed off isn't the route I'd prefer to go. One option I was wondering about was what the minimum heating system I can get away with that leaves me open to easily incorporating a SunAmp shortly after building control is signed off? Maybe an instant electrical hot water heater and a few two bar fires? But then there's DEAP (SAP equivalent) to contend with. Anyway, thought I'd throw this to the experts here and see if I'm stoking a fire to burn myself in or not?!! Thanks!
  17. Hi folks, Currently in the foundation and site preparation stage of a timber frame build. However we can't decide what to do with heating and cooling the house. So far we are having solar pv on house roof and garage roof as they are both SE facing so we will have a 10kw system. We are then going to have 3/4 of the downstairs as UFH and a log burner in the living room. In the bathrooms and en-suite's we are going to have some electric towel rails and then we were going to use an ASHP to make sure the air circulated around the house. So the problem we are having is that there is no heating per say upstairs other than the towel rails in the bathrooms. When we started the timber frame journey the above set up from several timber frame companies said it was fine to do it that way. But now as we get close to booking trades in firms are questioning the lack of heating upstairs. I currently don't have the design SAP as we are having issues get a PSI value for the thermal bridging. Timberframe company don't have it so our architect is trying to sort it. The u-value for our walls is 0.2 if that helps. So should we be looking at an UFH heating for upstairs in the bedrooms? Do we need a MVHR? 01 Elevation layout Architect drawing.pdf
  18. AndyT


    Hi, I have included this event as I did not see it mentioned elsewhere and thought it might be of interest to others on the forum in the London area. This is a free event providing you register first. Please visit . ecobuild 2018 says "it is aimed at the latest technology; the freshest thinking; and the most innovative materials to keep you at the forefront of the built environment." Might be worth a visit? Kind regards AndyT
  19. We have an open vented central heating system with gravity fed hot water. For reasons over which we will draw a polite veil, we (well 'I') drained the radiators, refilled them, flushed out what I could: and ............made the heating problem worse. At the very best time of year for that to happen. So, in a fit of rage and frustration, I re-drained the complete system took all the radiators off and, at long last, discovered what the problem is. I don't know what I'm doing. Anyway, here's the thing: 's gonna get cold in the next few days and I'd like to stay married. The 'boiler' is a multi-fuel fire. It has a back boiler which is now empty. Please tell me I can light the fire anyway, even though there's no water in the heating pipes. In other words use the fire as a simple space and running hot water heater...... If I can't there's a nice warm hotel right next to where SWMBO works, and .... well you can guess the rest.
  20. After a slight hijack on another thread, I thought it best to start one a bit more dedicated to heating control systems. Some of us like playing with wires and stuff, other are happy to buy in a system. This may be a good place to combine the pooled knowledge, and pinch a few ideas. If I get time today (decorating bathroom) I shall try and post up some thermodynamic theory. But no promise on that.
  21. I'm sticking this here as I've been asked the question via PM, and rather than just give an answer to one member, I thought it might be more useful to stick the answer somewhere were others can also read it. Back when I was first looking at doing some rough "what if" type comparisons, between different build systems, windows, insulation and airtightness levels etc, I wanted a fairly quick way to be able to change one element, say the wall U value, or the efficiency of the MVHR system, and see what impact it had on the overall heat loss of the house. This model was never intended as a substitute for something like PHPP, which is very comprehensive, it was just intended to give a rough idea so that I could see the scale of some of the changes, and work out where best to spend our limited budget. Having written the spreadsheet for our build, others expressed interest in using it, so I tidied it up and let others have a copy. Because lots of people seemed to want to use it, and also because it generally seemed to give results that were within 10% or so of more complex models, like PHPP, I put a copy of the spreadsheet up on our website, as a free download: This post is a set of very brief instructions on using this spreadsheet. First some health warnings. It was never intended to give an absolutely accurate prediction of heat loss, and as such it takes no account of solar gain, wind or incidental heat gain from occupants and appliances. As a consequence it is generally a bit pessimistic, in that it will usually tend to slightly overestimate the heating requirement. This is not necessarily a bad thing, as it can be useful to have a bit of heating capacity in reserve for exceptionally cold weather. To use the spreadsheet, you first need to gather all the data needed to complete the white cells. Most of this should be self-explanatory from the notes in each section. The U values, for example, should be the true U value of the component, including any additional thermal paths, so the window U value needs to be the Uw value, not the Ug value, and the floor U value needs to be adjusted for any thermal bridging around the periphery. All the areas are the internal wall, floor and ceiling/roof areas, not the external ones. The model does not account for geometric thermal bridging at corners, but in a well-insulated house this effect should be very small, anyway. Some of the most difficult to obtain data can be the mean daily air temperature and the mean minimum daily temperature, for each month. This data is available for your location on the Met Office website, but posting a link seems a bit fraught, as the Met Office keep changing their website and this makes any link out of date fairly quickly. All I can suggest is that you work your way through the historic data on the Met Office website and find that closest to where you live. Once all the data is filled into the white cells on the spreadsheet, you should get some numerical data in the green cells, plus two graphs will appear. The graphical data is often the most useful. First, there is a basic heat loss versus outside air temperature plot (the Heat Loss Vs Delta T plot). You can use this to determine how much heat the house will need to maintain the room temperature that you put into the spreadsheet (it defaults to 20 deg C, but you can change this to whatever you feel comfortable with). The red line is the total heat loss, the other lines are there so you can see which elements are contributing the most to the total. If you want to know how much heat the house will need in order to maintain a temperature difference between inside and outside of 20 deg C (say a 20 deg C room temperature when it's zero deg C outside), then just go up vertically from the 20 deg C point on the horizontal axis until it meets the red line, then go across horizontally from this point to the vertical axis and read off the heating needed in watts. The other plot shows the heat loss per month, and this one can be a bit confusing, because, like the other plot, it takes no account of incidental heat gain, from solar heating, appliances, occupants etc. The best way to use this is to print it off and pencil a horizontal line across where you think you wouldn't have heating on. For example, If you turn your heating off in April/May and on again in September/October, then draw lines across at about the point where these dates cross the other lines and call that your "no heating" point. The mean heating needed for each month will then be the difference between those lines and the values on the plots. You can quickly work this out by just noting the amount of incidental heat gain, indicated by the pencilled horizontal lines, and then subtracting those values from the monthly values. Be aware that this is really a very rough estimating tool, as there will be big peaks and troughs in daily temperatures within those months that will effect the heating required. In most respects, the heat loss vs delta T plot is more useful for sizing a heating system. Hopefully the above should make some sense to anyone trying to use this tool.
  22. This post appeared on ebuild, and since it is the work of many people, I reproduce it here. It's a shadow of its former self because I can no longer make the links to the comments to which the bullet points refer. Some you win , others you lose. So, because the text without the link is useless, I have deleted some references to the authors. I have not deleted the names of the original authors who registered with us in the hope that they can provide us with a link to relevant material The checklist is not definitive. Over time I will link this checklist to comments on (buildhub and elsewhere) which substantiate the point made. Your comment on this list is particularly valuable because any work done here improves the validity of the list. And so is likely to save you time and, hopefully, money. Heating Checklist Background reading and considerations Fundamentals Get a feel for what you already use Consider applying PHPP to the design to derive a heating requirement Use J S Harris spreadsheet{J, got a link to that for us?, Ian} Play with PeterW's FingerInTheAir MVHR Checker (PeterW#5) { Peter, got a link to that for us?} Heat Calculations Passiv? Do you need heating at all? Look for Thermal Bridges in your design How are you going to manage cooling? Consider Phase Change Material Storage. Stitching ASHP and UFH together On mains gas? No brainer - it's cheapest Cost benefit analysis. KISS Separate out DHW. Use instant water heaters Selling your house on? Higher temperatures needed? We are all getting older Higher lower occupancy rates in the future? Which thermostats to fit? Smart? Analogue? Radiator? It's not easy. But KISS - off the shelf. (jsharris Blog whole entry and discussion ) Underfloor Heating (UFH) DIY or not? End of lay (Nickfromwales#7) Plot the loops out on graph paper (TerryE#12) Best layout (NickfromWales#15) Useful summary (Alphonsox#17, and Nickfromwales commentary on that #27) ) How to deal with the pipes to the manifold before second fix Testing for leaks (declan52 #25) Avoid piping under toilet and sink traps (nickfromwales#29) MVHR By definition, MVHR = air tightness Forget a traditional fireplace, therefore. MVHR wishlist Where to put the vents? (jsharris#10 et seq) Keep pipe runs to a minimum (PeterStark #10) Minimise 90degree bends (PeterStark #1) Insulate all SUPPLY ducting (PeterStark #10) External Vents at least 2m apart (PeterStark #10) External vents slope downward (PeterStark #10) Fitting metal joists? Fit rigid ducting first (PeterStark #10) Supply to living and bedrooms (PeterStark #10) Extract from wet(ish) rooms (PeterStark #10) Mind yer bonfires ( jsharris#3) Location of MVHR unit Noise concerns: fit attenuation boxes (jsharris#11, jsharris#2) Type of ducting Radial design explained (jsharris#6, whole thread worth a read) While you are at it, try this (jsharris#6) Think through the cooling issue (jsharrisblog 38, 03:48, 1andR whole thread, jsharriswhole thread, TerryE, whole thread, hazymat, whole thread ) Bio Mass / Wood burners A cautionary tale (Steamy#1) The British Medical Journal on the subject (Steamy #1) Heat Pumps (ASHP GSHP) What's your heat load going to be? (Steamy#2, DeeJunFan#3) Are they worth it? (jsharris #4) Caution (jsharris as above) ASHP and DWH (jsharris #7) No need for DHW feeds to all rooms (jsharris#13) jsharris blog post(s) (jsharris) but see recent entries (part 41 and elsewhere) in relation to DWH Controls, how? (jsharris blog 38) Run slab from room stat? (jsharrisblog 38, 03:48) How to cool the house? (jsharrisblog 38, 03:48) Solar: Thermal or PV? FIT considerations RHI considerations Which Solar or PV? (Declan52 #1) PV for Hot water (recommended by jsharris, Ed Davies Blog, accessed Jan 2016) *But* consider separating out DHW. Use instant water heaters (jsharris#5) It's (PV) a no-brainer (Nickfromwales#6, jsharris#8)