Thermal bridging

[Paddocks532]

Hi all

Just when we thought we could crack on😥

Our sap calculation man has told us we've failed. He thinks🤔 because of possible cold bridging. He says he can't do the design for us we need to pay a professional designer😭 possibly costing £2000. Is this right. How can we overcome this quickly and do we really have to pay someone more money in the design stage. We've already been through the whole nutrient neutrality and buying credits etc which held us up for 3 years on top of all the normal stuff 😭

[Russell griffiths]

I don’t know what build method you are proposing, but if it’s a new house and you have failed the sap then you need to go back to the beginning and start again because something is very wrong. 
 

you either have an architect who thinks it’s 1960 or you have chosen a poor build method, 

 

How are you thinking of building this thing. 
 

please don’t say brick n block with 100mm cavity and 75mm mineral wool insulation. 
 

we all started somewhere, c’ mon show us what you got. 

[Paddocks532]

Hiya

Thanks Russell

No we're timber frame. Just about to put 220mm insulation + 75 ml edge insulation into our base over the next few days then dpm and ufh pipes then 100ml concrete slab in 4 weeks time. We will have a brick skin up to window height then black stained cladding on the top half, we are a single storey dwelling. We have lots of insulation everywhere😁💰+ mvhr, ashp, solar and a battery. One thing we haven't decided on is windows but looking at our budget already it will have to be a middle of the road to lower end price point. We have a lot of glazing but will be having shading on the south and west side over windows. I have to go to work but will put drawings on this evening.

[IanR]

From your January post you were up to ground level, so can we assume you now have your timber frame up?
 

Do you really have an issue or have you just not supplied sufficient info for thermal bridges to be calculated so worst case assumptions have been used.

Can you post a labelled section through the offending thermal bridges. Did an Architect do the overall design?

Added: re-reading your OP, is it possible he doesn't know how to calculate the psi values (hence you'll need a professional) and has just realised that the new SAP rules for cold bridging make using the default assumptions an almost definite fail.

Edited 19 minutes ago by IanR

[Paddocks532]

Hi Ian

Oh how I wished we were that far. 🫣 It took a long time to nail down a company to do our ashp, ufh, mvhr and solar package. So we're nearly ready to put in our insulation (which we've just had delivered this morning) prior to our concrete pour in about 4 weeks time. Probably the fact we haven't given sufficient info🫨. Yes an architect done our drawings. But can't remember seeing detailed drawings for these junctions.