All Activity

There is a bit of terminology to learn. Energy is measured in MJ (megajoule). A joule is the standard unit for energy and when converted to base units of kilograms, metres and seconds is very small. Why the M for 1,000,000 is added at the front. Now no one, apart from us nerdy scientists, use MJs, and domestic energy is metered and purchased in kWh. MJs can be multiplied by 0.0007778, or divided by 3600 to end up with kWh. The k just means 1000, W is watt and h is an hour, which is 3600 seconds. Power (W) is the rate that energy is used. You can think of this as your miles per gallon in your car, with energy being how many gallons are in the tank. If your car does 40 MPG at 60 MPH, and your tank has 8 gallons in it, you can drive 320 miles over 5 hours and 20 minutes. A unit of power is called a watt, which is actually a J/second. Again a small unit, so a k is added. A k is 1000. This gives the more normal kW for a power rating. Boilers, heat pumps and even wood burners all have a maximum kW rating i.e. 6 kW. Radiators, UFH and fan heaters also have a power rating. (This can get confused by some people talking old imperial units of BTU and BTU/h, but we went metric in ,'73, so tell them off) Where it starts to get confusing is a house will need a varying amount of thermal power to keep it at a steady internal temperature. This is caused by external temperatures rising and falling during the seasons and even during the day. This can be overcome in a number of ways. The easy way, and the way old heating systems were set up, was to fire up a boiler at full power, heat some water, pump it around the house to all the radiators, which then heated the air. When the house was up to temperature, the thermostat turned the boiler off. When the temperature dropped a few degrees, it turned the boiler back on. These days we are a bit more sophisticated and try to deliver enough energy to match the losses. This keeps the house at a steadier temperature, and used less energy overall. You will almost certainly read on hear about weather compensation (WC). This is just a basic feedback system that knows what the outside temperature is, how much power is being delivered to the house and for how long it may be needed. All that can be boiled down to a few numbers. The main numbers you need to know are the thermal losses for each room. Once those are added together, you get a number for the whole house. It is usual to size for a worse case i.e. -10°C outside. This gives you a maximum power requirement (heat source kW). Most of the time, you will be heating the house when it is way warmer outside, so the second number you need is about how much the heat source can be turned down internally. This is called modulation. Gas boilers have quite a high ratio, sometimes 10 to 1 i.e. 12 kW down to 1.2 kW. Heat pumps are not, generally, so good and are often in the range of 3 to 4 to 1. There are ways around this, but that is for later. The other thing that is important is domestic hot water (DHW). There are two ways to do this. Heat water only when it is needed (instantaneous), this requires a lot of power, often over 25 kW. Or Heat and store in a cylinder. This method takes longer for the same amount of delivered hot water, but used less power, often in the region of 3 to 6 kW. If the heat source is delivering both central heating and DHW, then this needs to be taken into account. With modern combination gas boilers, they are sized to deliver enough hot water, and rely on boiler modulation to deliver lower power for the space heating. Heat pumps, generally, rely on being only slightly oversized (which improves efficiency most if the time) and run a space heating time slot and a DHW timeslot at different temperatures and different times during the day. There is a lot of detail in heating design. So questions to ask are. Maximum house losses. Room by room heat losses. DHW reheat times.

It's not about complex maths. None of the maths involved is complex. It's actually pretty straightforward and it's not about box ticking here. It's just about good old transfer of heat. If you've got a low energy build, lets say 30W/m2 at design outdoor temp, your mean water temp in a screed floor is going to be about 29C, now consider what that needs to be when you're at the average outdoor temp of 7C in England. The mean water temp requirement is then below the required floor temperature to even produce heat into the space because there's then no MW-AT difference and it'll probably below the minimum flow temp of the heat pump. You then have to rely on controls to switch flow on and off, which we all know is not the way to be running a heat pump. TBH finger in the wind look at it and call it, is exactly why we're in the situation we're in here in the UK, because very few heating engineers and possibly M&E Consultants are up to basic design and so many systems are shite and inefficient when they don't need to be. Just a bit of maths and thought is all that's needed at the early stage.

Is it (expletive deleted)

How can this be true? If there’s no spares then you’ve zero other choice? Y branch cut in to existing run, a single socket 135° bend into that, and take the branch off to pick up the ACO. Standard practice tbf, and even if you did this with a foul connection it would still work perfectly well.

It won’t end up overheating if they turn the flow temp to a couple of degrees over the room stat set point. Can’t happen. I’ve been around enough of these types of projects to know this isn’t an issue, just lots of people like the complex math behind it all and then still just come up with the same conclusion. This really isn’t rocket science at all tbh, any any seasoned (and directly experienced) M&E consultant or ‘heating engineer’ (not the ones on their mothers side) should be able to just look at this holistically and call it. If it’s going to be an MCS certified job then it’ll just be about ticks going into boxes, and then the system fettled afterwards to perform to suit the dwelling based on real life experience in the actual address, and the occupants feeding back to the installer after a full 12 months of occupancy. Tick boxes don’t take the occupants own quirks or preferences into account, imho these are the most important factor but often get overlooked.

Congrats, must be an amazing feeling. I like the adjustable spot lights you've used, especially on the ceilings - what brand are they and where did you get them from?

Congrats, was a pleasure meeting you and your wife and it is a lovely property. You have done very well.

Yes, so they should be telling you that they'll produce a heat loss calculation based on your drawings and the SAP report you have. Then you should get a figure of a total output for the heat pump and a report telling you the heat load of each room and that will feed into a design of the underfloor heating (UFH), radiators, fan coils etc. If you're going for UFH on its own or with fan coils, keep an ear out for if they ask about cooling too, as that could be very handy for you.

Is it? If you have to start featuring something with the access chamber. Couple of slip collars and a y branch jobs a goodun and its legit.

And yet the pipes are all still at 150mm and no variation between rooms. Whilst we have seen the design we don't know the heat losses the design is supposed to cater for. If this is a properly insulated house with low losses and in particular low down losses, the 150mm spacing is frankly silly, It'll end up overheating the house and then the installer will start telling them they need a 1000l buffer or something to prevent the heat pump from cycling when all the actuators start closing down and it all unravels from there. Instead they could do a proper job of UFH design. But show us the design numbers and I'll be open to correction! 😉

It's whatever someone (usually a salesperson) can convince someone else of what it is. A client (spoiled brat 2nd wife of a wealthy old chap) bought an £1800 vanity unit (no basin and no tap) and a £400 extension drawer set to go on the end. 15mm chipboard, and probably £200 of materials / soft close drawer runners / labour involved. By the time there was a sink on top and a tap, the 'sink' had cost near to £4k. Just picking the drawer front up broke the corner off it, terrible design where the mouth of the unit and the drawer front were 45'd and then became ultra thin on the leading edges. Thin vinyl veneer (black) and light chipboard, so any chip or mark was instantly visible. Utter dogshit, and I've bought better off eBay for a 1/5th of the price. Said brat was told by the salesman that is was a high spec blah blah, and she told her new husband to stump up or life would be hellish. After a bit more shopping she'd blown nearly £18k on a bathroom suite and enough tiles to do 1/3 of the walls and floor. Most of it was available online for prob half the price or less, but she wanted the retail therapy and putting on a pedestal, so off they went to be robbed blind in broad daylight with a huge smile on (her) face. The other side of the coin is my sensible clients who want value for money, but not "cheap", so when I explain higher spec systems that come in more expensive than other quotes they have had independently, from their own due diligence, they see where the extra money has gone and appreciate the improvements in quality / longevity / comfort / etc and are then happy to pay the uplift between my quote and the ones they have; most systems are bean-counted to be competitive, so are quite vanilla in terms of initial offerings as most know they're competing against others who have priced off the same plans. The 3rd side of the coin is the minority who ignore my advice and reasoning, go for cheap as they are insistent they have done their own investigations (with no industry experience or actual real life knowledge) and then complain when the uninformed choices they made have backfired and cost more / delivered less etc. To these people who think they know better, I say "fill yer boots".....no skin off my nose!

Seeing them this morning. I just wanted to prep. We can’t find any installers in our area (see previous post). We have full SAP report (all 16 pages) which means nothing to me. Heat loss comes up a handful of times relating to different things, all different figures. I see other people quoting a single number … 4, 5 heat loss or such like so was expecting something similar to be on the report. This is worse than windows 😂

What are they talking about? Of course MVHR is taken into account in the designs and you can use whatever flow temperature you want as long as you can demonstrate in the design that the system provides the heat to heat the house properly. With MVHR you use the calculation methodology from SAP where the efficiency of the system is taken into account to calculate ventilation heat loss. This is really important because often ventilation losses make up more than the fabric losses. Where do these people come from? BTW I know this because I'm MCS Certified for design and installation of ASHP.

Shouldn't they be providing input? If they can't you need better installers!?!

https://www.screwfix.com/p/manrose-round-central-reducer-white-125-100mm/10684 You can buy duct tape, or get the large jubilee clips. https://www.amazon.co.uk/Kair-Metal-Hose-Clip-125mm/dp/B07ZPGVH4L/ref=asc_df_B07ZPGVH4L?tag=bingshoppinga-21&linkCode=df0&hvadid=79989677905430&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=42064&hvtargid=pla-4583589145554366&msclkid=eb0a5ca7b18819f05a0835004d2084ce&th=1

Apologies; I missed this. As @JohnMo said this was just generic filter material - I bought mine from https://www.justfans.co.uk/synthetic-air-filter-media-10mm-1000mm-1000mm-p-2037.html. I see it is listed as G3 whereas I thought I was buying G4 as per what was originally supplied. Either the page/product has changed or maybe I never was. I'm not too fussed either way as I've been using it for a few years and it seems to be doing the job.

I got them from a Paul Heat Recovery page at this link which, unfortunately, no longer appears to exist. This is a shame as it went into some detail behind multiple methods being useful, and explained it well along the lines of the other info that they still publish. Here are the calculations though: Method A Efficiency = 100 x ( SupplyTemp - IntakeTemp ) / (ExtractTemp - IntakeTemp) Method B Efficiency = 100 x ( ExtractTemp - ExhaustTemp ) / (ExtractTemp - IntakeTemp) Method B attempts to factor in unit insulation loss which can also include heat going into the unit from the surrounding area this artificially boosting the apparent efficiency calculated with Method A. I am probably explaining it badly, and always just used to refer the the explanatory graphic on the page that illustrate the addition heat flow paths that Method A doesn't take account of. Edit: Here's a somewhat similar diagram from a different site that shows the additional heat flow through the insulation: : With these figures, Method A gives 100x(19-5)/20-5)=93% whereas Method B gives 100x(20-8)/(20-5)=80%

My 5.5L V8 GLS 63 makes the same wonderful noise and is a lot quicker than 6.6 secs. Surprising that's as slow as it is for a hybrid, but I bet it's dialled down in the factory and is capable of much quicker; I expect they stop utter and outright abuse of the battery and drive train to promote longevity and reduce early failure etc.

Hi folks, my new home has a 120mm flexi duct connected to cooker hood that needs connected to a 100mm rigid pipe coming out of the ceiling. it was taped with airtight tape by kitchen fitters but it’s fallen off. what’s the correct way to fix this so it’s airtight? thanks

I doubt you'll be able to use that much insulation with a screed. You'll be removing a lot of volume of screed and by the look of where you pinch points are, you'll likely just have to leave them uninsulated. It won't matter one little tiny bit btw, so my advice is to step away from micro-managing this to death and accept that the flow temps will simply be so low you won't even know the UFH is on . If you have any pre(mis)conception of having hot sections of floor where the pipes group together, then you're going to be proven pleasantly wrong, as it just doesn't. Losing such large volumes of screed at very localised areas, especially at entrances to rooms etc, will be a bad idea and is something I actively avoid, so the way the pipes are bunched up are a bit daft and not how I'd lay it out. Living room should be fed from the utility and the pipes for those two loops taken under the partition stud wall, as that deletes 4 pipes from the first lot of congestion. Yes, people "frown" on pipes going under partitions, but the reality is zero ill effect as you're stuck to this project like velcro and can mitigate against any misadventure. Entrance hall needs to be completely reconfigured, that's just silly. Pipes can then be spaced equidistantly in the double doorway leading into the kitchen / open plan room. Close, but no cigar I'm afriad.

Gas is gone within 15/20 years, it doesn’t massively impact the performance.

Well I have been pleasantly surprised by the UFH supplier - they understood my request to increase the spacing between the supply / return pipes, replace the utilities area and have re-done the design. Where they're still bunched close, I'll insulate so that there is an exposed pipe every 150mm. Here's the revised drawing for those who will be interested. UFH-FHW CAD Drawing Rev 2.PDF

No tow bar. A mate was going to get the same as mine but decided not to as he wants to tow. It feels funny only going into garages now for Ginsters and wine gums mind.

I don't think my 4.4l V8 range rover is much slower and I bet it makes a nicer noise whilst doing it. Do you have a tow bar? 😆

SAP is about calculating energy use not about sizing the actual heating system or emitters (Radiators / Underfloor Heating / etc) . But the new standards for heat loss and system design do use aspects of SAP (e.g. designed or measured air permeability). You do need a heat loss calc and system design.