First full self-build!

[Rishard]

@gravelrash- Certainly is worth the few hours labour for that kind of saving. The same applies to the whole build, the more you can do the more you can save. When I go to the http://orlimex.co.uk/ website it comes up with international plywood supplies. Is this the same company? Cheers 

[gravelrash]

43 minutes ago, Rishard said:

@gravelrash- Certainly is worth the few hours labour for that kind of saving. The same applies to the whole build, the more you can do the more you can save. When I go to the http://orlimex.co.uk/ website it comes up with international plywood supplies. Is this the same company? Cheers 

I dealt with Christopher Hirst  email-  Christopher.Hirst@orlimex.co.uk

I had a qoute from another uk company that was cheap https://basalt.tech/products.html#rebar i think but came in 50- 100m rolls (33p/m)....and seemingly the roll is under a great deal of tension...maybe they would cut on site before shipping?

Edited February 18, 2022 by gravelrash

[Rishard]

On 14/02/2022 at 23:28, Iceverge said:

I paid €800 to a guy who in hindsight did a half assed PHPP for me. 

 

After that I downloaded the manual and started playing with it. Most of it doesn't need filling out unless you are getting certification. It would easily save it's price (about £150 i think )

in optimising insulation.  We ended up at 200mm EPS floor, 250mm EPS beads in the cavity walls and 400mm cellulose in the attic based on an hour spent checking where our € made the most difference with phpp.

 

 

Jeremy's spreadsheet gives very similar results but doesn't calculate overheating which can be significant. 

 

 

If you just want to know you max heating load and you are planning on building   thermal bridge free + airtight+ MVHR  then a simple calculation will do. Just measure the outside of the house like PHPP not the internal. The internal heat gains from electrics etc cancel the MVHR losses and other sundries. 

 

 

 

(External Floor area * U value)

+

(total external wall area * U value)

+

(external roof area * u value)  

+

( Window area * U value) 

 

 

 

Add them all together and multiply by your maximum temp difference you'd expect on a cold day. 

 

 

(114m2 *0.16)

+

(232m2 * 0.13)

+

( 114m2 * 0.09)  

+

( 30m2 * 1) 

 

= About 89 * ( 20 deg difference in the south of Ireland)  = 1780 W total heating load. PHPP gives 1497W. Either way a 2000W heater will do ( and is doing) the trick!

 

 

 

 

By the way we didn't bother with a stove due to dust and smoke inside as well as the trouble getting them beyond passive levels of airtightness. 

 

 

 

 

 

 

Having done this on my build now it looks like a 2kw heat source would work. I’d be happy to amp it up if required. This was fairly surprising as I calculated my form factor at 4. I did put in 300mm in the floor walls and roof mind. 
 

Out of interest I did the same calculations for a barn conversion I did which is under 1/2 the size. The form factor came out at 4.6 and is 80% new build work with only 100mm cavities. The 30m2 of wall which is uninsulated I adjusted the u-values. The heating requirement was similar to my project. Does this sound right? I guess in the barn conversion it wouldn’t consider the thermal bridging issues and air leakage? This conversion was before my understanding of airtight/bridge free design. I know the windows and doors wont be to the high level install spec they could be with tapes ect. What would you say all of these factors would contribute to that overall heating requirement? How long is a piece of string I guess? 

[Iceverge]

What m2 is your house? 

 

That basic calc is only really vaild for MVHR, airtight and thermal bridge free. If you start running up to high leakage and areas of poor insulation all bets are off. A windy day will effect a non airtight (+windtight) house tremendously. What does your barn use in practice?

 

Be careful of overestimating window performance. An small opening passivhaus certified window with a centre pane U value of 0.5W/m2K can quite easily end up with an overall installed U value of 1.5. 

 

Lessons learnt from the forum and personal experience.

 

It's best to size your heating system to allow for.

 

1. Off peak E7 heating (the house structure/slab can buffer the heat for non E7 hours)

2. To allow DHW as well as space heating on cold days. 

3. To avoid heat pumps running at max capacity and low efficiency, icing problems etc. 

4. Not too large that your boiler is constantly cycling on and off. 

 

 

Don't over complicate your heating system in a passive house. If you can feed in some energy somewhere central it'll be enough to keep everything ticking over nicely. We just use a £30 plug in heater at the moment from about 17:00 til 08:00. The house is between 20-21deg.  It seems to make little difference where the heater is placed so long as the doors are open. 

 

 

 

 

 

 

 

 

 

 

[Rishard]

@Iceverge- our ground floor is 147m2 and is planned as a passive house quality build. My friends barn however is not. Built to building regs and is yet fully functional so he won’t have any idea till he starts trying to heat it to work out his usage. I guess the above calculations wouldn’t apply as you state. 
 

I’ve been reading a lot on here regarding active slab heating options which I feel could be a good way to go. Having young children I guess that my heating will fluctuate a lot more than others. Likewise with DHW. I’m happy to seek input on this. I like the idea of the low capital cost of the Willis heater for a slab if I can arrange a solution for dhw. Again growing children may influence this decision. 
 

Is the fan heater your main CH currently? Do you have any other system in place? 
An ‘ease of use’ system would be preferable like you say without over complicating things. Coming from a joiner talking plumbing ?

[Iceverge]

19 hours ago, Rishard said:

Having young children I guess that my heating will fluctuate a lot more than others.

 

It's an entirely different concept of heating to a conventional house. Fluctuation doesn't happen really. It will eventually drop to about 14 Deg if unoccupied. Even after a day of a powercut during the big storm recently the internal temp was still at 20c. 

 

With hindsight I would have liked to have put UFH pipes in the floor slab. Maybe buried in 150mm-200mm of concrete.  The more the better I reckon in this case. You could defo store enough energy from E7 to heat the house all day. You would be able to run the slab at a very low temperature too which should make any complex control systems unnecessary as well as maximising the COP of an ASHP. 

 

19 hours ago, Rishard said:

Is the fan heater your main CH currently? Do you have any other system in place? 

Yes. No. You need to keep on top of it though. If you miss an evening heating the bathrooms might end up at 19deg which feels cold. 20-21 is fine. 

 

 

We use almost exactly 10kWh per day with 2*adults 2*small children DHW. All heated E7 in a direct UVC. From memory about 1kWh of this is losses from the direct 300L UVC. It works out at 260L per day of water at 40c. 

 

The heat pump payback on DHW is much longer than space heating as the SCOP drops from about 4-5 to maybe 2.5-3. One thing I would say is to fit as large a cylinder as you can. 300l works fine but with guests we need to heat outside E7 hours. A larger cylinder can store the same energy at a cooler temperature too so will have lower losses. 

 

Plumbing isn't rocket science. I replumbed our place after the plumber made a hash of it. Hep2O is an excellent system and very user friendly. 

 

( If I was to do it again) 

 

1.  UFH in a thick slab. One zone.

 

2. As large a water cylinder as possible. Maybe a giant 600-1000l coil in tank thermal store. This would avoid G3 requirement and the need for a seperate Willis heater for UFH.  It would allow easy ASHP connectivity with no buffers etc.  ( Beware ASHP and smaller thermal stores are not a good mix to the high water temp required kills the COP)

 

3. DIY plumb it. It's very doable. 

 

 

 

 

 

 

 

[Rishard]

Excellent. Is the large thermal store you mention something different to an uvc? Am I right in thinking this is just for dhw and not the ufh? There are a few options floating by around in peoples experiences. It does seem that a small ashp would still be suitable to cover both ufh + dhw. Is this your thoughts? I feel a diy pv system would also benefit this style of set up. I’m mainly seeking advice on the type of system which would best suit the build. I guess overall capital investment has a part in this and also simplicity.

[Bitpipe]

Lots of discussions on space heating but you really need to consider overheating as thoroughly.

 

Our passive standard house is in SE England and the single UFH zone on the GF comes on for maybe a handful of weeks each year. We have electric under tile heating in bathrooms (for comfort) and wet towel rads. No heating in basement and nothing aside from the afore mentioned bathrooms in first floor and rooms in roof.

 

House is always comfortably warm in winter - frequently get a shock when we wander outside in a t-shirt.

 

Everything that generates heat (people, appliances, pets, solar gain) will contribute to your requirement. MVHR will prevent internal heat being wasted via ventilation but is not an effective provider of heat per see as the air volume moved is quite low. 

 

Spring, summer & autumn are the challenge, once any unwanted heat gets in it is very hard to shift and low sun in spring and autumn can be very effective at heating the house unintentionally. Xmas day was warm this year, having guests and the ovens on made it necessary to open the sliders

 

We face east (street) & west (garden) with gables to north & south (so minimal glazing there). We have external motorised Venetian style blinds to all east windows and recently added internal motorised blinds (from Ikea) to the big sliders on the west. West bedrooms have balconies so are a bit stepped in from evening sun and have normal curtains. All velux on east and south have external motorised shutters, west velux have internal blinds.

 

Effective use of the blinds is key to keeping house comfortable in summer, we do stack ventilation in evening /overnight (opening atrium velux and opening & locking a slider a crack) which is very effective also.

 

PHPP was done by a project manager early in project - as well as giving peace of mind wrt space heating it flagged the overheating risk.

 

Some here have a passive GF slab (i.e. insulated underneath) with UFH pipes cast in and use their ASHP in cooling mode in summer, keeping slab just above dew point.

 

I regret not putting in provision for split air con as with the roof PV would have been a free cooling solution for summer.

 

 

[Iceverge]

5 hours ago, Rishard said:

Is the large thermal store you mention something different to an uvc?

 

Yes, an UVC keeps all the DHW At 47-70 approx. Any water expansion is taken care of by an expansion vessel and over pressure cases by temp and pressure release valves. It requires a qualified person to install and inspect it annually. (although many don't bother). There is a worst case situation where all safety devices fail and it explodes.  You can draw almost all of the stored water inside off as useful hot water as the cold water in the bottom won't really mix with the hot water being drawn off. 

 

 

A thermal store is a large tank full of water that will never see the light of day. It is heated by your heat source directly in most cases. A DHW coil passes through the tank which absorbs energy into the DHW so it emerges hot, cooling the large body of water in the process. No safety or over temo devices required. Worst case is with a huge boiler you could end up boiling the store and it would vent as steam. Not terribly realistic.  No issues with DIY install or maintenace. Disadvantage is that you need to store either a lot more water or water at a very high temperature as once  the temp of the store drops near to 40 deg it can't supply hot water any more. A thermal store at 45 deg will have almost no DHW capacity. An UVC will have lots. 

 

With a Thermal store you can run UFH heating directly from the main water body in the tank. 

 

The short answer is put in UFH and a large (300l minimum)UVC and an ASHP so long as it's not huge money (<£6k). Its the soundest advice I can come up with. 

 

 

 

Edited February 28, 2022 by Iceverge

[Rishard]

@Bitpipe- I hear your points on over heating and has probably confirmed my inclinations regarding running phpp. Our house is likely to be shaded by surrounding properties during lower winter sun and we don’t have huge areas of south glazing. We do face south so would feel more comfortable having had the solar effect on the house looked at. It’s very easy to forget over heating in midwinter living in a draughty house! I like the ufh cooling method too using the heat pump. It certainly adds more interest knowing it can be used as a cooling tool. What runs your ufh? Can you use it to cool the slab? Is an aircon split something which can work with the mvhr or a separate system? 
 

@Iceverge- I’d not heard of a thermal store. I also like the sound advice on ufh and an uvc teamed with ashp I guess the next bit is pv to help it all along. Do you run your system on e7? Or do you have help from solar along the way and batteries ect. I guess once you have a electric system to sensible thing is to invest in pv. I’ll have to price up all of the components to see what overall costs would look like. I originally planned the same system but with a gas boiler in mind years before I got to planning. That was based on the price of both a gas boiler and cheaper gas. I hear your point on gas boilers delivering high heat quick which seems unnecessary in PH. Prices are also heading north so initial spend may soon be paying back quicker. Are people getting much from their pv over winter? 

[Bitpipe]

2 hours ago, Rishard said:

@Bitpipe- I hear your points on over heating and has probably confirmed my inclinations regarding running phpp. Our house is likely to be shaded by surrounding properties during lower winter sun and we don’t have huge areas of south glazing. We do face south so would feel more comfortable having had the solar effect on the house looked at. It’s very easy to forget over heating in midwinter living in a draughty house! I like the ufh cooling method too using the heat pump. It certainly adds more interest knowing it can be used as a cooling tool. What runs your ufh? Can you use it to cool the slab? Is an aircon split something which can work with the mvhr or a separate system? 

 

So we don't have that system as we built a passive basement (no heating) and the UFH is under the suspended timber GF. We also use a gas boiler

 

@jack is probably a better person to ask as he has an insulated GF slab with ASHP and does the cooling effect in summer.

 

MVHR should be thought of as efficient ventilation, not a core way for heating or cooling the house, although in a highly insulated and airtight house it can make a difference - key issue is the volume of air moved over time. MVHR airflow is normally relatively low (30% of fan speed) , increasing to boost (50% of fan speed) when you're using a bathroom or cooking and want stronger extraction. Air is a poor carrier of heat (or coolth) so the small volumes of air moved around are fine for ventilation (reducing CO2 and moisture, smells etc, introducing fresh external air) but not super meaningful for moving heat around. MVHR is also usually restricted to the temp of the external air but you can add heating and cooling elements in the airflow.

 

A split aircon will blast cold air out so is best considered a separate system. 

 

 

[Iceverge]

We don't have a system, just one of these. 

 

 

In Ireland so it's not E7 per say, but a similar concept. No PV.

 

Shiny gadgets are fine but remember they will break down in a few decades max. Often before they've recouped their capital cost in a low energy house. Good design and good fabric will last for centuries. 

 

Do PHPP. A collegue told me recently of a completely glazed WSW gable on their house, new build, Bregs. It regularly reaches 35-40 deg if they don't open windows. They're looking at a fairly strong 4 figure sum to install blinds internally which will only partly mitigate the problem. 

 

Southern windows are not the issue, Overhangs/brise soleil easily sort midsummer overheating. East and West are much more problematic and really require external movable blinds. 

 

Do you have plans to share? Do you have planning permission?

 

 

 

 

[jack]

45 minutes ago, Bitpipe said:

@jack is probably a better person to ask as he has an insulated GF slab with ASHP and does the cooling effect in summer.

 

There are lot of threads discussing this. I personally wouldn't be without it.

 

Here are a couple of example threads:

 

 

 

 

 

 

 

 

[Rishard]

@Bitpipe- thanks for linking jack and likewise, thanks jack for the links. Like I mentioned, I had planned for a gas boiler based on its lower cost. Cost plays a big part in this. I feel either a cheap ashp could work or a regular gas boiler with ufh. Or at least the provision for one or the other. Maybe if I don’t go down the ufh route then having a cooling system would be wise. 
 

@Iceverge- I love the low tech approach. Does this provide heat into all rooms such as bathrooms. I know people are tending to have a towel radiator in the bathroom as a heating source. With our project I worked with a local architect who I have a good working history with. Although he is not a passive designer, he was very willing to learn and take advice. We had a few sessions with bill from the green building store which helped a bit towards our thinking and some design aspects. The house faces south towards a conservation area which limited our design a little. The north faces the garden, the best aspect. We have no west glazing and very little to the east. The plot dictated our location a little and it will be shaded a little by neighbouring buildings during the winter. We compromised a little of form factor vs style I guess. We made it through planning and feel happy with the look. Some of the internal walls/spaces may change a bit but we labelled up plant room/airing cupboard ect to dedicate at least some space in the house. We are happy to make some changes to these once I have a good grasp on how much ‘plant’ we will be looking at. 

[Bitpipe]

We went gas as at build time since it was cheapest and it works fine for DHW and space heating (the latter requirement is minimal).

 

However we could upgrade to ASHP in the future should the economics change, maybe think on that - a bit of tactical ducting and power planning at this stage would cost little and leave the option open for the future.

 

We also have low power (150w) electric under tile heating in the bathrooms, mostly for comfort as tiles will always feel cold underfoot due to their higher thermal conductivity. Was inexpensive and contributes a bit to the heating requirement.

 

Your lack of east glazing will help minimise morning solar gain but you need a strategy for the southern aspect - blinds (internal or external) etc

[joe90]

1 minute ago, Bitpipe said:

However we could upgrade to ASHP in the future should the economics change,

A very good move, flexibility

2 minutes ago, Bitpipe said:

Your lack of east glazing will help minimise morning solar gain but you need a strategy for the southern aspect - blinds (internal or external) etc

I was told my south facing conservatory would over heat our new build but it’s not happened, in fact it heats the house all by itself fir an extended period of the year. I have green netting ready to hang inside it if we get a very hot period but in 5 years it’s not happened yet. Only last week the conservatory got to 30’ on a sunny day when it was chilly outside but it saved the heating from coming on for the rest of the week.I can, with a bit of work, reverse engineer the ASHP to cool if necessary.

[Rishard]

@Bitpipe- I thing gas is still low initial and running cost. It’s a big investment in ashp/pv ect. I’ve attached a site plan also to show some of the other buildings nearby which will add to some of our shading. I’d be interested to see this all in a 3d model to see where the sun hits throughout the year. I think leaving provision for electric and plumbing connections for ashp would be wise. I guess it isn’t possible to cool the ufh I summer with a gas boiler set up? 

 

@joe90- is your conservatory part of the main building/airtightness envelope? 

[joe90]

17 minutes ago, Rishard said:

is your conservatory part of the main building/airtightness envelope? 

No, with all that glass impossible to meet regs on insulation etc, It has a dark floor and slab over insulation (to capture heat for the evening) and I have bifolds into the kitchen diner and the lounge so when the temp out there is above 21’ I open then all up and heat the house, in summer if it gets above 21’ I keep them closed to stop the house overheating and open all the doors and windows in the conservatory to let the breeze in. It works well.

[Iceverge]

On 01/03/2022 at 22:24, Rishard said:

Does this provide heat into all rooms such as bathroom

 

Yes. It's remarkable really. It's almost like an absence of cold rather than heat though. Maybe towel rads would be nice in the bathrooms for point heat. We have spurs just in case. However I seem to be be somewhat obsessed by this and find myself making spreadsheets with 30 year coat benefits analysis of the merits of a €100 towel rad. It probably means it's not too much of an issue.

 

I have a lot of time for bill butcher. His denby dale videos are excellent. 

 

Plant is an open question. MVHR, UVC plus plumbing. Electrical box. No real reason they need to be colocated however. A thing that bypassed me was there is no need for a hot water cylinder upstairs. Originally I was planning a thermosyphon boiler cooker and in later designs the cylinder just got left there. It would have been better in our utility. Keep the MVHR easily accessible. Filter changes are important. 

 

 

 

 

 

 

 

 

The areas I highlighted above could be quite tricky to install thermal bridge free. Timber frame in cavity wall construction. 

 

The sticky out bit with a steel to support the upper wall will be almost impossible. 

 

Timber frame, EWI or ICF are your friend here. 

 

 

[Rishard]

@Iceverge- your right, these are the tricky bits. They were raised in our discussions with bill. We did flesh out a few ideas but would be good to iron them all out while I’m at this stage pre building regs ect. For the steel carrying the upper block work above the rear extension we planned to have thermal block work above the steel up to the roofline insulation to reduce thermal bridging downwards. Thoughts? I’m happy to draw out some details. As for the main gable which continues up above the 1.5 story, I haven’t worked out the best solution for this yet, as you say EWI could work. Or timber frame this gable section up to the ridge. I would need to speak with our SE about some of the loading for the ridge though. Hoping to use gluelam for the ridge. Also, the constructions is block/cavity/block based on cost per m2 and other build really reasons. Even as a carpenter by trade I’m choosing blockwork however I can lay block too. Just to complicate things further we’re planning vaulted ceilings with provision for a few ‘on show’ trusses to help with our spans and add character. This makes the gable insulation detail pretty tricky but I’m sure I can find a way. Would love to know if others have worked through any of these details. 

[TerryE]

On 16/02/2022 at 17:57, Iceverge said:

Ideally using a board to catch the morter drops.

Try this 😊

 

Also picking up @Iceverge comment.  You will see in some my blog posts that I ended up using this sort of approximation.  Worked fine and let me play with design trade-offs on elements and construction techniques. You really need to get U-values under 0.15 or so and have decent (e.g. triple glazed) fenestration. This involves avoiding thermal bridging by design, and as Iceverge says, going TF for the inner skin just makes everything so much easier.  

 

Another factor is that once you are in this sort of thermal domain, air losses rapidly dominate so you need to go for that ~0.5 ACH target  and MVHR.  It is really rather hard to get this sort of air tightness with a blockwork inner skin, especially if you have dot & dab boarding out: you are really too dependent on the quality of the bricky's work.

 

Spending a few days following through other build experiences here will save you a lot of tears and money. 

Edited March 3, 2022 by TerryE

[Rishard]

@TerryE- hi terry, thanks for your comment. I’ve read through your blog and admire the approach and results you achieved. Our block/cavity/block is full fill insulation. A technique I’m very familiar with having built this way for years. The masonry approach is a lot cheaper for me being the main mason, my brother being the other. Our labour is technically ‘free’ and blockwork is £10m2 single skin so has a huge sway on design. We plan to attack airtightness with wet plaster much the same as the Denby dale build. Again, we both lime plaster most of our jobs so have no issues there. We are planning 3G windows doors ect and mvhr. We really need to focus on our heating:cooling which has been discussed and also some of these thermal junctions @Iceverge has rightly raised. Our discussions with bill butcher also raised these so we have had some discussion on them. One of our issues with either purchased timber frames/sips/icf systems was the cost. I’m aware of the benefits with all these systems as I believe they do all have their place but for our project it comes to cost. I wonder if a spandrel panel could work from the wall plate upwards to get around some of the thermal bridging issues. 

[TerryE]

19 minutes ago, Rishard said:

The masonry approach is a lot cheaper for me being the main mason ... We plan to attack airtightness with wet plaster much the same as the Denby dale build.

 

Wet plaster is a big help, and I can understand your reasons for adopting a familiar construction technique, but you also need to address the main vulnerabilities that can lead to bad thermal bridging / air loss.  A couple of examples:

• The inner blockwork is on the warm side of the thermal gradient.  You don't want a thermal bridge to the ring foundation that carries it.  Using something like Perinsul Foamglas blockwork for the couple of courses that span the FFL will dramatically reduce the bridging.
• Don't mount your joist direct into the inner blockwork leaf, but rather place in wood fillers when blocking up and then fit and seal joist hangers during first fix. This way you avoid all of the airgap risks.

I am not saying this is the best way for you and your brother , but what I am saying is that you need to identify the risks and decide on construction approaches before you start the build rather than putting in retrospective mitigations.

Edited March 3, 2022 by TerryE

[Rishard]

@TerryE- I appreciate your points. We have had the passive principles in mind from the start. Your recommendations are spot on too. These are 2 crucial details along with several others we plan to use. I have plenty of time still to get my detailing arranged before we start. Most of which we have followed from denby after consultation with bill. 
 

After all these discussions I’m keen to push on with phpp. We had planned to have the green building store do this for us however they are very busy for several months. I still feel this would be valuable to do at this stage. I see some people have built without running phpp which was what raised the question. 
 

 

[Iceverge]

4 hours ago, Rishard said:

Even as a carpenter by trade

 

 

Stick frame on site in that case, cut out the cost of the timber frame factory. 

 

 

Outside to inside. 

Brick or cement board. 

Ventilated Cavity. 

Breather membrane. 

T&G woodfiber sheathing board.

Cellulose filled structural stud. 

OSB racking board taped as airtightness. 

Battened insulated service cavity. 

15mm Soundblock plasterboard. 

Skim. 

 

BELLISIMO!!! 

 

It's a very robust way of building.

No membranes for airtightness to get punctured.

Excellent windtightness (Often gets forgotten).

Woodfiber deals with bridging. Importantly around windows and doors. It a very tricky junction with block.

Fully breathable so very low chance of rot. 

Negative embodied energy.

Minimal wet trades.

Service cavity to make follow on trades a doddle. 

Excellent decrement decay.

Able to test and rectify airtightness as you go leading to really top ACH scores. ( almost impossible with block) 

Pumped insulation guarantees full fill. 

Permits a really chunky upstand to the floor slab. Performance of passive slab with the cost of a strip foundation. This junction is a really tough one with block. 

 

 

Don't underestimate the time and cost of detailing a block house to passive levels. It took me almost a week to make and fit OSB boxes around the window. Airtightness was probably another week, very sloppy and really a hope for the best affair. Cleaning the cavity ties took 2 days and mega skinned knuckles. Chasing and coring for electrics and ducts was insufferable.