SBMS

Might be worth asking your timber frame manufacturer if they have psi values. why timber frame out of interest? Have you considered masonry or had any quotes yet?

Your build will almost certainly fail minimum sap requirements using the default values. That’s pretty much why they removed ability to use standard details. We went to our cavity insulation provider and their in house team calculated all the requisite psi values for most of the E values. Warmcel Then provided psi values for many of the R values. most sap providers will want custom values and won’t chance ‘making them up’ as they may face audit. what’s your construction makeup? Ours was a 200mm cavity so there were t any readily available.

They do actually fill small to medium holes as well during the blower. Their initial blower tech will indicate where they are so they can help with filling them up. The mist then does the smaller holes and effectively replaces the need for a parge coat on inner blockwork by sealing it. They also provide consultation at the outset of how to do your wallplate junctions, chamber floor junctions etc 👍

Think it was near 5.7m. Wouldn’t do that again.

Also - don’t do B and B floor. Hated it on last build. Flush thresholds are difficult (can’t cover air bricks). Some of the longer spans make the crockery ‘jiggle’ when my kids stamp on the floor. Probably could have been improved with smaller spans but we are going slab this time.

My makeup: walls - brick and block, 200mm cavity eps blown beads a- 0.15 u value floor - 200mm pir (two layers of 100mm) - 0.09 pitched roof - 304mm posi rafter, cellulose blown insulation with 22mm wood fibre sarking and medite smartply as inner airtight and vapour control - 0.11 u value flat roof - warm roof, 200mm PIR over 225 posi joists with medite smartply again - 0.10 u value SAS aluminium windows and doors average 0.75 Uw value SAS sliders and bifolds average 0.9 Uw value MVHR throughout wall hung floor posi joists with passiv purple around hangers (just in case) aerobarrier throughout target 0.6 ACH ASHP with downstairs UFH. Currently deciding between fancoils upstairs or traditional rads with AC units for cooling. Spent a fair amount of time detailing the above and I think it represents a high performing traditional masonry buildup. Would be wary of things like PIR in your roof. Whilst theoretical u value is 0.11, I doubt this would be achieved unless you’re all over fitting. And even then wood shifts and gaps open up. Opting for things like pumped beads and cellulose designs out any potential issues with workmanship - even the most diligent builder might have a crew on a Friday afternoon that rushed something. You’ll live with that Friday afternoon job forever. Have a look at your thermal junctions as well. Make sure where your roof and walls meet is continuous for example (beads and blown cellulose work well for example here). Check or design your thermal junctions at doors (thermally break across your cavity for eg don’t use concrete fill cavity to sit your doors on. It’ll bridge. ) Learned a lot on last build and have tried to design out my mistakes from last time!

Congratulations! Appreciate @Alan Ambrose’s points but from my experience the conversation between planning officers and planning consultants is fairly reliable. I would say if they’ve indicated they will pass it, your parish council were supportive and you didn’t have any pertinent objections it looks like a reason to celebrate. I remember the feeling, so savour it and get ready for the hard work! 😂

Why did you get the a2a? For cooling?

Does your a2a supplement an ASHP or is it your sole heat source?

Agreed. We’ve already decided to use aerobarrier for the interim testing and then the actual sealing. They work for me the client (often the testers are getting whatever the builder needs them to get) so we will have this check and balance to ensure we get the level I’ve designed and want to achieve.

Have you picked a fan coil unit? also - what happens if the units are cooling and then the DHW program starts?

Thanks @joth do you have fan coils yourself?

Does all flow and return pipe work need lagging as well if running cold water through?

Pretty much as title says.. considering fancoil rads for our upstairs again instead of a ducted AC system… would like to use them for cooling as well. Does each fan coil need a condensate drain for cooling?

Agree to a certain extent @TerryE but a 90k price differential? That’s a lot of spare money to spend on airtightness detailing.

Contractor should have registered them with relevant utility authority - as laids they are called. So one for electric, one for gas, one for telecoms, one for water etc.

Hi @CaptainDram - we did, I got a quote from MBC, a local SIPS supplier and erector and a brick and block quote from a builder we have used before. Like for like, to get to a shell for a 380m2 shell: MBC Timberframe: 0.14 walls, 0.1 roof - £178,000 MBC Timberframe: 0.1 walls, 0.1 roof, 0.6ACH- £223,225 Brick and Block - 0.15 walls (200mm EPS beads cavity), 0.1 roof (Warmcel pumped) - £132,000 Brick and Block - 0.15 walls (200mm EPS beads cavity), 0.1 roof (Warmcel pumped), 0.6ACH - £136,000 Both need windows, foundations, floor insulation, face bricks, render, slates etc so those prices are pretty comparable. The Brick and Block 0.6ACH includes £4k for aerobarrier who will similarly guarantee that air tightness level. It was a bit of a no brainer really as I was erring on the side of masonry anyway as I just like 'solid'. Also - you can really get in the weeds with U values. I did a heat loss calculation and 0.15 walls is roughly £990 per annum in heating (ASHP). 0.1 walls (the passivhaus version form MBC) was roughly £930 in heat. Thats a payback of over 1453 years. Law of diminishing returns when it comes to insulation!

Yes. We had 8 buildings and couldn’t evidence one of the buildings (stables) being used for its ‘intended purpose’. Was easier just to exclude it as we were claiming self build exemption anyway. But the council are definitely all over it.

I would treat the costs as less than 50% of your ground floor sqm costs. You’ll be putting a roof on anyway and with attic trusses they can come with a posi floor. Minimal changes there. You’ll need an extra staircase and then really it’s internal fit out costs.

I’m pretty sure it’ll be treated as a trading activity which means you’ll fall under income tax not capital gains. If you’ve purchased land, built a house and are selling it brand new you’re effectively a developer and therefore this is trade. might have been prudent to have done the transaction inside a limited company but if youve done this with personal funds I think any gains will be treated as income and taxed at your marginal rate. You’ll also have to pay national insurance on this net income. You could also rent out the property for a ‘bit’ And then sell. CGT might be justified then as you could argue your intention was investment not trade. Weirdly I think taxation treatment here is subject to your ‘intention’ and what can reasonably be inferred as to what you intended to do.

@CaptainDram - it depends what you're after, but I always think maximising space in a plot like yours would be where I would go. A really simple layout but if you go for a regular rectangle box with a fairly normal ridge height, you could use attic trusses which gives you 5.5m wide rooms in attic space (with eaves at 1.5m). A simple 11.5 x 9.6m footprint would fit in your site and would give you a greater footprint than your design (110m2 versus your 96m2 ). In total I think you could get 270m2+ of usable habit space with a standard 8.5m - 9m ridge height house (drawn onto your scaled plot).. Ground Floor First Floor Second Floor

Not three stories but rooms in the attic. Ours is a two storey house but with clever planning we had three floors with some really good usable space. What’s your footprint sqm with what you’ve designed?

I think you would do better to regularise it into either a standard U shape or an L shape. Also consider going up into the attic space to fit additional bedrooms so that you don’t have to compromise your plot space. I reckon three stories in a simple L shape would yield more space and less cost.

That’s really interesting @JohnMo - it looks like I’d need roughly 40 watts per sqm to do no upstairs heating. That’d be pretty wide spacing and still maintaining a low flow temperature for the 29 degree differential. I wonder what spacing they would ordinarily use. It’ll Probably be over specified.

Yes that’s my worry. I guess if they spec an emitter size for rads I can just guide them to installing a fan coil. What if the UFH needed a higher output overall (say 4kW instead of 3kW when they had the as built, because air tightness went to s**t) than the loops were designed for? Are you saying they would just increase flow temp? Is that suboptimal as opposed to reducing centers and putting more pipe in?