Iceverge

No problem. I'll give you 50p but I must subtract the cost of the stamp from that.

HURRAY!!!!! Interesting, I would love to stick frame a house. Mainly because I just love hammering bits of timber together. There were large aspects of our masonry house I hated with the dust and the hardship that TF avoids. What other method would you like?! Good people are always worth paying. Bad people are worth paying to keep them away. Depends on how fast you are blockwork. One mason built out house with no labourer. Icf Always stuck me as the wrong way around.nsoft on the outside and hard on the inside. Like a Dime bar when what you really need is an Armadillo. TF or masonry I think are the best.

Chimney?

Based in your design constraints a section like this would be much more buildable. No steps in the upstairs. 45 deg roof into a 3 deg section in the middle for sanding seam. likewise with the dormer. 400mm allowed for the walls and roof for plenty of insulation.

In general once stuff is inside the main insualtive layer then it's not worth worrying about extra minute thermal gains like insulating padstones or the like. As i can see you'll have 150mm EPS beads outside your UB so any gains would be very small. I would stop the inner leaf of the wall 100mm short of the external wall and allow the 100mm PIR to oversail the wall and meet the wall EPS beads. This will make a thermally very nice junction. In general I'm not a fan of too much steel work in domestic construction. It's hard to finish and fix to with typical builders tools. I would prefer precast concrete or on site poured lintels for the blockwork sections and gluelams for the roof. They're aesthetically quite nice in my opinion and leaving them on show may be cheaper and easier than building in a UB. In general the more I look at your house I can't but agree with @Gus Potter. There's a lot of obstacles to getting it to the standard you hope. It has the classic hallmarks of something that perhaps began more simple but had bits bolted on to satisfy a desire for something different or with a bit more flair. Then it sounds like planning appeared and imposed some limits that compromised the building. 1 went through 3 sets of planning permissions before we build our house. Each one simpler in turn and it was still a pain as a first time builder to get anywhere close to the standards I wanted with efficiency etc. Would you consider returning to the drawing board and designing out some of the trickier bits like reverse slope dormers and hidden guttering?

................... sprints to trophy cabinet.........🏃‍♂️🏃‍♂️🏃‍♂️🏃‍♂️🏃‍♂️............... .........unpacks golden framed airtightness cert................ ............. Yells "I told you someone would care" at nonplussed family........ .......Tear runs down cheek.......... Tears of joy, tears of pride ..... .......Children roll eyes and crank up some yank making funny with the Minecraft on TV......

No problem, I have a layer of 50x25mm battens running up the rafters and closely spaced 100x25mm running across under the Standing Seam roofing. I 'm really not a fan of Ply in this location hard against the metal roofing and risks trapping some moisture between the ply and metal that spaced timber avoid. They deal much better with long term exposure and heat cycling than sheet materials too.You'd be saving 7mm by going to 18mm ply. You may be able to get down to 100x50mm timbers at closer centres if you ask the SE. It's not impossible but it'll make little difference in the grand scheme of things. In any case I would aim for 400cc to keep the spacing inside ok for plasterboard. Don't get lured into using imperial OSB 8x4 at 16" centres outside as it won't match the metric 1200x2400 plasterboard inside. Completely fine so long as you have a very robust airtight layer in the buildup. With the PIR above the rafters the dew point will only reach the timbers at -1 externally. In the UK its massively unlightly to be less than this for more than a couple of weeks a year and with no convection through the structure (pucker airtightness)you'll never have an issue. Against the OSB. Full fill will ensure this. Yes, it'd be fine unless you're relocating the house to the north pole. Dew point will never come in enough or for long enough to cause any issues. With this you don't need service cavities anywhere as the airtight layer is outbound of the studs. Just run wires through the rafters. No i absolutely did! 1. Frame the roof 2. Sheath with OSB and apply VCL and seal. 3. Cover EVERYTHING in PIR and then breather membrane. 4. Battens 5. Cladding 6. Wireing internally then mineral wool then plasterboard and skim. You may want to think about when you install windows and penetrations. I would do it after the VCL and before the PIR so you can make good the air barrier before the PIR is applied. I would suggest you run 100x25mm battens vertically over the cladding to distribute the thrust forces. You can use 200mm screws horizontally and then a 25mm screw at 35deg incline to take the vertical load of the batten. You'll need to drill pilot holes but this is easily done if you first make a long drill bit and make up a jig for the angles. Fiber glass could work but it'll be expensive and harder to source than off the shelf materials. You wouldn't get as good a thermal envelope either, especially around windows as you'll need to use the vertical battens to secure any external header and jamb trims.

An excellent improvement. That corner seal in the window is a bit gash though. I'd be having a word with the window man. Having gone to the hassle of manually doing this it's like climbing Snowdon and seeing there was a blasted train to the top when you arrived.

200mm composite panels would be an excellent solution. I have no idea why we don't use them more. Snobbery I expect.

Almost but not 100%. You will have some moisture in there no matter what you do, be that from the timbers or a shower of rain during construction. You need to make sure your buildup lets the moisture out somehow. That can be inwards or outwards as required.

I would add soffit vents on in the eaves and some slimline mushroom type vents in the roof to keep a good flow of air above the breather membrane. It doen't need to be over the top though as all it is doing is allowing the roof battens to dry. It's not dealing with buckets of warm moist internal air like old fashioned cold ventilated attics.

Ok i think I have an idea. In simple terms... Frame the whole structure as required by you SE. Probably site built looking at the drawings. Start at the wall plate. Next sandwich a VCL. Something tough like this. Drop on the rafters. Terminating them at the wall plate. Continue framing the entire roof in this manor with timber sizes as demanded by the SE. Then sheath the enitre roof in 11mm OSB to carry a peel and stick OSB. Return your eaves and gable VCL segment to the main roof and the internal wall to form a complete airtight layer. This will give you an excellent chance at getting a continuous airtight layer. Use the same method for the dormer roofs and cheeks too. Ensure you return the VCL to all windows and penetrations too. Add your rafter tails and gable overhangs. cover the entire roof and dormers with a layer of 100mm PIR. Cover the roof with a roofing membrane, everywhere including the flat bits and dormer cheeks. Doesn't really have to be breathable but something with self adhesive strips would help as you'll be fitting on top of the PIR. Mark the locations of the rafters carefully before and with 185mm screws tie 50X25 battens into the rafters. Add cross battening to create a ventilated gap and support the metal roofing as required. You can then add 100mm of mineral wool between the framing and rafters for a U value or about 0.14 over the whole roof. The most important thing is that you will have a great chance at airtightness and with the PIR externally you'll have excellent thermal bridging. If you have the space you can add more PIR as required externally but you'll need longer screws obviously.

@Tony L Looking at your build-up it's a fairly complex shape. Two things spring to mind on how your building will potentially fail and rot in future. 1. Airtightness , Damp air will be carried by convection into the structure by poor airtightness. 2. Thermal bridging. The damp air will condense and rot the timbers. Good news though, both are readily solved with some thinking. 1. Do your airtighness outside the structural elements of the build. 2. Externally insualte the roof. This will make it very simple to get a good air barrier and avoid any cold bridging.

What kind of metal have you covering the remainder of the roof and I might have a go at a detail later. Also a section view would help.

I've very much gone off the idea of GRP and EDPM roofs stuck straight down on top of OSB and the PIR like all warm roofs are specced. The GRP is your only barrier against the elements and it's subject to the full rigors of heating and cooling and the associated expansions and contractions. The roof surface could quite easily see a 60deg temp swing over 24hrs in early summer. I very much fear this will lead to leaks down the road for too many roofs. I would far prefer to see a metal roof over a ventilated cavity over insulation over rafters.

Welcome to the forum. Congrats on a nice house. Tell me more about the construction method planned? I would certainly avoid any PIR in between the studs of a timber frame in any case. Blown cellulose gets my vote instead.

@flanagaj Good 2g will be better than bad 3g. Pay attention to weather and espically air sealing. Thermal bridging through the frames too. If they're all A1 only, then have a look at the centre pane U value.

images.mp4

I wouldn't panic, The window and door frames, especially the sills will be the thermally weakest part of the house. There's only so much you can do to insualted them as you need to deal with water shedding as a primary concern. Therefore they're the the coldest and the first place to gather any moisture. As soon as you get some heat into the house and some mechanical ventilation I wouldn't be surprised if the issue disappears.

Floor covering makes a lot of difference. Carpet and LVT throughout here. Efficient UFH with a floor at 25 deg won't feel much different on your toes from a well insulated slab at 20deg. Not chilly, not hot. UFH in a high flow temp situation is very nice on your feet but it's expensive to run. Cost and complexity?

Passive class house here, not certified, no UFH. An actual measured heat usage of 3200kWh or 17kWh/m2/annum. Supplied by an electric plug in heater. It worked fine so long as you plugged it in anywhere downstairs and allowed it to gently input heat for 18hrs/day. Expecting it to batch heat on TOU tariff overnight wasn't as successful as i had hoped. it needed to be turned on at about 17:00 in winter to keep the living rooms warm enough(21deg). I added some electric heaters in the bathrooms for comfort as 21deg isn't quite toasty enough. Fan heaters are better than 2 Bar quartz heaters. The house is very comfortable. I replaced the electric radiator with an A2A HP for 2025. It's dropped our heating consumption to very close to 1000kWh or 5.5kWh/m2/annum. It works fine so long as you give it long enough run times for the heat to disperse around the house. It won't be quite as cheap as an A2W HP as you can't batch heat a slab on TOU tarriffs and a COP of 3 to 3.5 won't match a top end A2WHP. However it only cost €1500 installed so there isn't much in it. Add DHW demand or solar and the sums would change again. (FWIW an A2W + UFH was quoted at €14k in 2020) TLDR: 1. Anything will heat a passive house comfortably if you're prepared to give it a fair chance. Short run times and quick runups won't work with localised heat sources. 2. A2W HP's are best for comfort and running costs. However they only have the best long term costs if you can get a well priced install.

I think Aereco had the original design. As I understood it it's just a strip of nylon that expands and contracts with humidity. 20Pa really isn't that much. 100000Pa is 1 Bar or about 14psi.

Yes, humidity sensitive vents. https://store.beamcentralsystems.ie/products/dcv-intake-air-valves?srsltid=AfmBOopO9UvLROCeVYnm2p6C6nY5d6-wDWRsDgu2zj1VFhr6o6XYlf0p They're not cheap though and would go a lot of the way towards a full MVHR system. You may find it acceptable with just well set passive vents. You could start there and upgrade them if you found them too drafty.

Can you get an accurate split for your DHW vs Space heating? What are your motivations, cost or environmental or tinkering?! All are valid but it might help to frame an answer. Have you considered an ASHP to do "baseload" heating and "free" cooling in summer on PV? It might tick all 3 boxes.

A point people miss with airtightness is the role it plays in keeping damp air out of your walls and ceilings with the knock on effects of interstatial condensation etc. If you want a durable building you must control the air leakage through the structure. This is of course in addition to it's comfort benefits and energy savings. Regarding ventilation theres essentially only two types. 1. Holes in the wall and hope for the best. Be prepared to be overventilated in gale and underventilate otherwise. 2. Continuous mechanical ventilation, with or without heat recovery. MVHR is the most comfortable, uses least energy. It's not cheaper than other forms once you take filters and servicing into account. PIV,dMEV,MEV,DCV are all the same thing with little nuances. Just sucking or blowing air in/out. All will give you adequate quality air if set it up correctly. Unfortunately unlike MVHR you still need holes in the wall which may be drafty on windy days. @Eastfield have a look on search for @Thedreamer who heats their house with a stove and uses an ESHP for DHW and ventilation. An elegant solution I thought.