Eliminating thermal bridges - new build

mrsWhippy

Hi there,

There is a lot of emphasis on eliminating thermal bridges in a new build. How can I ensure that our design takes this into consideration? Am I correctly presuming that this detail is included in the construction drawings?

If our architect follows current building standards, are cold bridges going to be eliminated by design? Does the builder need to be on board as well, or is this purely detail that's outlined on the plans and followed by the construction company?

From my understanding, they typically occur where
-Floors meet the wall
-Wall ties
-Window sills
-Anywhere else??

I know this is basic stuff, but don't want to leave anything to chance!

Thanks a million

ht9zni1gs28crp

This should come out with the construction details from the Architect, but I guess the conversation needs to be had with him/her to discuss the level you go to. Either to meet current regs or beyond it.

The builder may have priced to meet current regs and nothing beyond it. Double check.....

mrsWhippy

Thanks Miller.

Do current regulations only eliminate a certain number of the thermal bridges, or all of them to less of a degree?

sydthebeat

mrsWhippy wrote: »

Thanks Miller.

Do current regulations only eliminate a certain number of the thermal bridges, or all of them to less of a degree?

minimum compliance currently is in accordance with the acceptable construction details

however i would always advise that construction drawings include all construction details to reflect the exact methods and specifications .... and not in general as the above details are

EmmetF

sydthebeat wrote: »

minimum compliance currently is in accordance with the acceptable construction details

Correct me if I'm wrong, but you don't neccessarily have to use the ACD to achieve min compliance, although it wouln't make sense not to (sorry for the double negative). Minimum compliance is achieved by acieving a min CPC and EPC value on the DEAP software (along with min. U-Values for individual elements).

By default, the DEAP software penalises all your U-Values for a new build with a value of 0.15W/m²K due to thermal bridging. So if your wall acieves a U-Value of 0.12W/m²K, the software makes this 0.27W/m²K. When you build in accordance with the ACD, you can reduce this penalty to 0.08W/m²K which makes an enormous difference. This penalty can be reduced further to as low as 0.02W/m²K with calculated thermal bridge factors - though I won't go into this.

Building in accordance with the ACD or better should be your first port of call in a new build before deciding on levels of insulation, triple glazing, heat recovery etc.

sydthebeat

EmmetF wrote: »

Correct me if I'm wrong, but you don't neccessarily have to use the ACD to achieve min compliance, although it wouln't make sense not to (sorry for the double negative). Minimum compliance is achieved by acieving a min CPC and EPC value on the DEAP software (along with min. U-Values for individual elements).

By default, the DEAP software penalises all your U-Values for a new build with a value of 0.15W/m²K due to thermal bridging. So if your wall acieves a U-Value of 0.12W/m²K, the software makes this 0.27W/m²K. When you build in accordance with the ACD, you can reduce this penalty to 0.08W/m²K which makes an enormous difference. This penalty can be reduced further to as low as 0.02W/m²K with calculated thermal bridge factors - though I won't go into this.

Building in accordance with the ACD or better should be your first port of call in a new build before deciding on levels of insulation, triple glazing, heat recovery etc.

techincally correct i guess...

but for the vast majority of cases achieving compliance with a 0.15 thermal bridge factor will be practially impossible.... so unless the client wants to pay for specific thermal bridge calculations, the 0.08 factor allowed by the ACDs is a must.

mrsWhippy

Thanks all.

So should the specifics in the ACD document be included in the construction drawings?

sydthebeat

mrsWhippy wrote: »

Thanks all.

So should the specifics in the ACD document be included in the construction drawings?

the problem with the ACDs is theres not many "specifics" in them to be included. Your architect should be supplying the construction details to comply with their requirements

to take one small example, in detail 1.04 at a concrete floor junction, the air tightness barrier is shown as a 'notional' blue line carried through the slab. Obviously that cant happen.

youtheman

Only thing I would add is just berceuse your Architect specifies a certain construction detail, don't just assume the builder is going to adopt it. A lot of builders do things "the way they always do it". I was building an extension a few years ago and I went to town on the insulation. I specified '2 inch HT Armaflex' for the CH piping insulation. I came in one evening and the builder had poured a new concrete floor over the pipes that had a different type of insulation. When I asked the plumber why he used it he replied "because that's what we always use". So he had to dig up the floor to do it properly.

So remember...."paper never refuses ink". You can have all the fancy construction details you want, but you need to make sure the builder follows them.

mrsWhippy

youtheman wrote: »

Only thing I would add is just berceuse your Architect specifies a certain construction detail, don't just assume the builder is going to adopt it. A lot of builders do things "the way they always do it". I was building an extension a few years ago and I went to town on the insulation. I specified '2 inch HT Armaflex' for the CH piping insulation. I came in one evening and the builder had poured a new concrete floor over the pipes that had a different type of insulation. When I asked the plumber why he used it he replied "because that's what we always use". So he had to dig up the floor to do it properly.

So remember...."paper never refuses ink". You can have all the fancy construction details you want, but you need to make sure the builder follows them.

Argh, this whole thing stresses me out. Trying to find out who is responsible for what, who signs off on what and when!

Our architect will PM the build - so i'm assuming he'll be the one signing off on all the builder's work. I suppose the key is to find a reliable builder in the first place, who understands how to achieve the level of airtightness and detailing that we're looking for. PM any recommendations please!

MicktheMan

mrsWhippy wrote: »

I suppose the key is to find a reliable builder in the first place, who understands how to achieve the level of airtightness and detailing that we're looking for.

Got it in one!