@converse

Do you certify?

The elements that I would expect to be potentially reducible in your list are the thin joint block work and the SIPs roof.

Ferdinand
PS I would be interested to be in touch direct, but there are no PMs here. BUt if you create an account on buildhub.org.uk, there is a PM system.

Posted By: ferdinand2000PS I would be interested to be in touch direct

You can “whisper” your comments to somebody. Put their user name in the “Whisper your comments to” box when replying. Only they, you and the forum owners can read the comment.

I expect a few people have already whispered a reply but I thought I'd make this public for general reference.

Posted By: SteamyTeaDoes the PassivHaus Institute, or whatever they call themselves, still specify the types of fridges/freezers, washing machines, dishwashers, TVs that they find acceptable to have in a property?

PHI doesn't specify them, never has as far as I know, but they do want to know what you've got so they can estimate your overall energy use.

Personally, I think it's a mistaken policy, both philosophically and practically. The units can be changed five minutes after certification (or may never even exist unless somebody bothers to check). The primary energy side of PH is much less impressive to me than the [main] fabric efficiency side.

Posted By: converseThin joint in my experience has worked both well and also not so well, and I can't really explain why. Some bricklayers just can't get the hang of it.

Why use a skilled bricklayer other then for leveling the first row?

How often do you get block cracking? And how do you stop your air-tightness render from cracking?

<blockquote><cite>Posted By: SteamyTea</cite><blockquote><cite>Posted By: djh</cite>
Personally, I think it's a mistaken policy, both philosophically and practically. The units can be changed five minutes after certification (or may never even exist unless somebody bothers to check). The primary energy side of PH is much less impressive to me than the [main] fabric efficiency side.</blockquote>How I always thought of it.
Bit like owning a Prius, but commuting though town in an old XJS</blockquote>

100% agree. You can easily buy a more energy efficient fridge, but fabric energy improvements are much harder to make once a house is built.

I can only speak for the Celcon blocks. We use their standard blocks, but they also do a super lightweight version which we don't use.

We have always put floors in as soon as we get to joist height, and we also use proper joist hangers as we go, rather than cutting them into the blockwork afterwards as some people do. You'll need to support the floor from below if you are going to use as a working platform.

How do you know if the render cracks behind the plaster board?
I don't. But I've go no reason to assume its going to, and the thin joint blockwork itself is pretty airtight even before it is internally parged and then externally EWI'd. Think about it, you have 10mm of reinforced synthetic render, on top of pretty airtight polystyrene glued and pinned to the blockwork, then the 215mm thin joint blockwork, internal parging, and sealed edge plasterboard = I really don't think theres going to be a major issue for airtightness. Bigger issues are window penetrations, windows and doors and service pipes.

Why are you using plaster board rather than normal plaster over the renter?
Easier and cheaper to get a good finish. People don't expect to see cracks at all in plasterwork these days, and plasterboard reduces the risks.

How are you getting a good air tightness where your joist hangers go in?
Well they don't go all the way through the blockwork - just relieve the blocks a bit by the metalwork and be extra careful with the blocks on top to make sure there is a continuous seal of thin joint adhesive all the way round.

I would say that while we are careful and sensible about getting as airtight as we can, there is absolutely no way any house is going to be 100% airtight, no matter how long you spend taping and sealing. Our airtest results are very good compared to most modern houses, but are definitely an area where we could improve by spending extra manpower. But I think we're about as good as it is cost effective to be.

Spec is under 2.5 and they've all passed eventually. That's pretty good I think, though the airtester told me he'd done a Passivhaus that he'd measured at 0.4. That's for the old spec houses which had trussed roofs. I'd expect the SIPs roof versions to be slightly better, or as good for less work.

m3/(h.m2) @ 50Pa

Checking the figures, results range between 2.0 and 2.5. I'll let you know the SIPS versions in a month.

You don't really get much time in an airtightness test. They really want to be in an out. The really big obvious leaks I've had have been a boiler flue that hadn't been installed very well, and a twisted loft hatch - both pretty easily fixed. Everything else has been lots of really insignificant leaks that add up together. These are really hard to fix in short timescales, so you have to make sure you are ready before they arrive. I'll probably buy a fan at some point so I can identify big leaks in advance. In fact, it might even cost in to do our own testing.

Shame the normal hire shops don't have airtightness testers on weakly hire.

Converse, a test using smoke before you fit your plaster board may show where the leaks are, some of the new air-tightness "rubber" paints could then be used to fix them. If only these paints where cheap enough to use instead of render....

DJH, agree that some basic checking first is a good idea. What we really need is someone to make a cheap simple blower door kit to get the house depressurized - I'm more interested in finding leaks than measuring them tbh, so the test equipment itself is much less interesting.

Posted By: converseDJH, agree that some basic checking first is a good idea. What we really need is someone to make a cheap simple blower door kit to get the house depressurized - I'm more interested in finding leaks than measuring them tbh, so the test equipment itself is much less interesting.

If it come as a kit with a smoke generators and detailed instructions on how to find and fix the leaks it could do a lot of good. Ideally it would cope with a full size blower door along with a convert allowing it be fixed to a open window, so the door can be tested as well.

Funding such a hire service could be a very good use of grant money.

I presume you 'suck' and wander around inside the house with the smoke pencils?

Posted By: GotanewlifeI presume you 'suck' and wander around inside the house with the smoke pencils?

I think that's generally easiest (assuming 'suck' means depressurise). In tricky cases I believe it can be better to fill the house with smoke and 'blow', then see where the smoke comes out.