U Values For ASHP With Sunamp

[Onoff]

A colleague at work has commissioned a 5 bed detached new build in Cambridgeshire. Architect designed.

 

I put him onto Sunamp and he's going for that along with an ASHP.

I'm a little worried though as when I spoke a while back with him about the importance of air tightness and insulation levels he was a bit blase saying the architect was dealing with all that.

 

Just a bit worried it'll get "traditionally" built by "traditional" builders. No offence but thinking back to when @Hecateh had issues with the insulation around her windows, almost the builders not caring. Someone else on here I think had them skimp on airtight tape. Is there then a checklist of points to watch out for to ensure it's as airtight etc as it can be. I can find out the construction if it helps. I imagine there's minimum U values it'll be designed for but are there better values he SHOULD be aiming for?

 

Cheers

[Dreadnaught]

@Onoff, this might be a good introduction: https://passipedia.org/planning/airtight_construction

 

And this from Bere architects might help for more detail: https://www.bere.co.uk/research/airtightness-report-a-practical-guide-to-achieving-airtightness-in-passive-house-buildings/

 

Personally, I found this book, Passive House Handbook, to be helpful, if he likes reading books:

 

Edited October 6, 2018 by Dreadnaught

[Declan52]

Is it block and brick or timber frame??

[Onoff]

27 minutes ago, Declan52 said:

Is it block and brick or timber frame??

 

Can't remember. Will find out.

[Onoff]

On 06/10/2018 at 09:21, Declan52 said:

Is it block and brick or timber frame??

 

Brick and block. He's not sure on the cavity width etc. Expecting the drawings this week. I mentioned the Passivhaus concept, his initial reaction was "councils are less likely to approve aren't they?"

 

Anyone with a Passive build in the Cambridgeshire area? This will be his "forever" home.

 

Going to send him the link to @PeterStarck's blog to try and convert him!

 

Cheers

Edited October 9, 2018 by Onoff

[Declan52]

Is he going for a full on passiv build or as close as to it as the budget will allow??

Cavity width will be a big decision. You are looking at a min of 200mm for this. What's is he filling the cavity with?? Beads is the easiest option, let the brickies build and then it's easy to keep the cavity clear so it will be fully filled with beads when the time comes. 

If he isn't sure on his cavity width you can build the founds 450mm wide to buy him some time. Then he can make it up to a max of 250mm wide. It will be a trade of between how much extra insulation beyond 200mm will cost Vs the real world benefit. The wider you go the more expensive wall ties become. Then you have extra work closing the cavity around doors and windows.

He could have a play around with Jeremys spreadsheet to see what difference extending the cavity will mean.

After that then it's using good quality windows and doors. No trickle vents or letter boxes. Using tape around these to sort out the airtightness. 

Making sure no trades rock up and start putting holes in the walls. Big no no. All your services need a lot of planning put in so this doesn't happen. Ducts in the floor all need put in when doing the founds.

All the junctions in the house, floor to wall, wall to ceiling all need specific detailing to stop air leakage.

Depending on the type of house you might need some sort of membrane for the roof. 

Wet plaster on the walls to seal them up. 

All the conduits all sealed up. 

Anything that penetrates the plasterboard like cables for lights all need sealed up.

 

Loads more but these will get you started!!