SBMS

You’re not way off, that seems very expensive.

I think it’s achievable with that budget. We were roughly £5k for up RIBA stage 4 (drawings for planning) and then another 4500 for the full drawing package. This is with a small boutique architect firm of 4 architects. Fantastic job, they did spatial modelling, massing of the building (in a 3d clay). They designed the whole house in a 3d game engine from the start so we can interact with it. We even did a VR session in their offices where we walked through the design and snagged any issues. It was pretty amazing. We benchmarked another architect practice that was well known and did similar things and they were a similar price. I would be asking questions like what technology do you use to produce designs. Both the firms we looked at build the model in a 3D engine (effectively unreal games engine) and this was a key thing. It meant we didn’t have to pay for ‘renderings’ or visuals. We had a link that we could jump to in a browser as we iterated on the design to walk around the house in detail. Other architects we talked to were clearly using more antiquated techniques, CAD tools etc but for us the use of technology in the design process was great. That and the usual flare for good design, comfort with innovative use, a wide portfolio of designed houses, comfort with one off build design and a design language that correlated with the type of house we were looking to design. And I refer back to the earlier point that this was all under 10k. So definitely do able.

Is that 10k to get you to planning drawings or to a full Building regs/builders drawing pack?

There's a local company near us that do a 195mm SIPS panel that achieves 0.13 U value. Or a 140mm that achieves 0.16. https://flitcraft.co.uk/injectawall/ Out of interest, have you modelled the difference between a 0.16 and a 0.1 u value? Its about a £80 in additional energy costs per annum when modelled for our build (YMMV, but its worth checking).

Have you looked at a thicker SIPS panel to do away with the 25mm insulation?

Which aspects of the spreadsheet do you think are inaccurate or not achievable? It sounds a bit defeatist to plan the construction of a build but ‘accept’ the quality required to bring that build to reality is not achievable?

Thanks @TerryE, makes sense why your overall energy input is lower. We just seem to be coming out with a high energy requirement per sqm which I’m struggling to reduce down. Even dropping walls to 0.1 and removing all glazing doesn’t help. One figure that does shift the needle is the internal volume as it’s 950m3. But I would expect as your floor area increases as does your volume so wouldn’t expect to get 390 sqm in a smaller volume (we optimised the house design for this, with rooms in the roof). ultimately it probably doesn’t hugely matter as the energy input is acceptable. Am just intrigued as to how a reasonably large well insulated, airtight house can hit the PH energy per sqm target.

Got you thanks. Is my understanding of the passivhaus recommendation for kWh per sqm correct? I wasn’t sure whether the kWh per sqm figure was adjusted for the heat source (eg if using an ASHP then the energy input would actually be circa 3.5x lower). If not I’ve no idea how one could get to a 15 figure using Jeremy’s spreadsheet anyway. It’s not that I’m arbitrarily aiming for that figure but it’s something that gives some context to energy requirement when assessing u values, insulation depth etc.

Ah! So the passivhaus level of 0.6 is not the target here? I assumed that ACH on the spreadsheet is the target measure of airtightness (or, I guess, a result of the level of airtightness?)

So the ‘air changes per hour’ column is not the airtightness figure?

Thanks. Glazing wise that includes a vaulted rear window, 2 storey glazed entrance and 13m of sliding doors. I put all the glazing into a single column in spreadsheet. As said though, even removing glazing doesn’t make a massive difference. 2 sets of French doors and a side door make up the doors. is 0.75 bad for air tightness? I know 0.6 is passivhaus so thought I’d target just above? Am I correct with the kWh per square meter figure?

Have been having another play around with the heat loss calculator. Have a couple of questions - I have plugged in the following numbers: We have a fair amount of glazing, but to be honest it makes little difference if I remove all the glazing. This generates an annual heat energy input per annum of about 14,000 kWh. If I take this and divide it by internal floorspace (circa 397m2), the energy per sqm is about 35 kWh per annum per sqm. Passivhaus stipulates less than 15 kWh. Even if I removed all glazing doors and rooflights, this shifts it to about 24kWh per sqm but still significantly out. Am I missing something? How would this figure be achievable? Am I reading the heat energy input values (row 84) correctly? I just added them all to get to the 14,000 kWh figure. Be really useful if anyone can share their calculations @TerryE think you mentioned on an earlier post an 11,000 kWh energy input. Am trying to figure out what moves the needle to get such a low input value?

I did try that but I noticed the u value difference for cavity widths they published weren’t linear? So assumed there was more to it?

Has anyone got the u values for standard cavities for EPS beads in a cavity (eg ecobead platinum), for different cavity thicknesses? have found some numbers but most stop at around 200mm or 225m cavity. Wondered if anyone has them for 250mm, 300mm?

For those self builders that went with traditional masonry/brick and block and aimed for high levels of airtightness, what was your ACH figure? Trying to get a sense of what’s achievable with careful detailing!

Company near to us offer a 192mm panel that is 0.13 u value if thats not too big?

Was after the price per sqm for the kit/superstructure, not the finished article.

@JohnMo have you got an aversion to TF? You prefer masonry? Genuine question out of interest as still looking at all options.

Interesting what you say. One of the perceived benefits of off-site TF seems to be speed but all the manufacturers seem to quote 16-20 week lead times. There’s a lot of house to be built in 5 months; I suspect the total build timeframe between different methods works out the same. @Gus Potter would you choose TF (stick built on site I assume) over masonry if building your own?

Yep completely agree. They’ve done our design and phase 1 and have been excellent. I think it’s pretty decent price to be honest and hopefully helps give some context to the OPs price which seems a bit bonkers 👍

If of interest just had our quote back from our architect of 4500 for full drawing back and submission to and liaison with building control.

We are just about to get a quote for our drawing pack and SE will update on here.

Brilliant.

Did you do beam 3 to avoid curtain glass? Are you cladding the front of it or doing it in brick