gravelld

Someone should create a spreadsheet to work out the sweet spot... is it doable with given space heating loss and DHW requirement?

Thanks for the update, let us know when you have the electricity usage (what's stopping you reading the meter?)

You'll enjoy the eaves if you have some scaffolding do it from outside. Best to use tape everywhere, foam won't last forever. What you doing about pests? Another way to look at it long term is that really the best solution will always be a warm loft with insulation outside of rafters and air tightness layer somewhere inbound of that, so if you have that vision then you could pass on the membrane for now and just do the basic work, everything else you have suggested: downlighters, service penetrations, ceiling/wall junctions etc.

Good point. Probably the reason my theory never took hold. I think forced air movement is the obvious way to go. One other interesting topic on this that comes to mind is that if you have a DIY rig you can move it around the house, sealing it against internal doors (assuming a hard floor to seal against). Might help pinpoint troublesome rooms.

@CrofterI've often had a similar theory about sealing up making other issues more obvious, I think the problem with that is you're still at the mercy of "natural" pressure differences (i.e. the wind). EDIT this editor is driving me mental, is there a plain text one? I think it's ideal if you can rig up a test system. What I would say is that you can leave the actual measurement until later.

Another ductless option is Lunos, but more expensive I think. Not sure if this helps when Googling but these units are often called SRHRV.

That's good to know, although given our house is CW we'll not see a penny (unless Onoff and his fiendish and dangerous longtermist ideals infect innocent Government minds). I couldn't even get them to fill the cavities on a Government scheme, so just paid for it myself. At least I got to choose the insulant that way (apparently on the schemes they tend to use fibre... I prefer EPS bead myself).

Government could do it, it just depends what it wants to spend its money on. But we're talking many billions nationwide. Would you rather have HS2 or healthy homes? I think I know which one would benefit productivity and ease the strain on the NHS more.

Do you think these schemes will allow best practice like: - Insulating down to foundations - Installing windows in the insulation layer - Taping and sealing correctly - Consideration to ventilation requirements of the property ? I'm a bit cynical about that. Whenever I see existing ECO work it looks like it has been done as fast as possible, plinths left exposed, cold bridges at windows, then a whacking great air brick because someone got worried about ventilation and no-one thought to design that in. And regarding cavity walls, don't even think about sealing cavities after insulating the external skin on government schemes; according to these schemes, anyone with a cavity wall has good enough insulation already (nonsense of course).

Yes, in fact for most it's probably the only way it can be done due to cost. See http://europhit.eu/ The trouble with that is, you just end up with the house done to not as good a standard as could be done, so large opportunity cost. I suppose it depends how long the house will be standing afterwards.

Yes, the horizontal overlaps of felt.

Holy crowded website Batman! Do they have details for high performance, e.g. windows boxed in insulation layer, or is it just bog standard stuff?

LOL, pretty much, at least some form of calculator. Just because it's an extension doesn't mean it cannot be modelled. You'll have to use an assumed figure for air leakage I guess. But maybe someone can also give you a yes or no based on their experience. The absolute temperature looks low to me, but I guess that might be because of works going on, doors open, closed etc.

What do you mean by ok? If you mean is the house performing to expectations then we'd need to know the design - the heat loss calculations produced beforehand.

That's all fine. I think I didn't parse your sentence correctly. I think I read it without that first comma, thinking you meant *all* internal spaces have no drafts to the extent that would affect the conduction:radiation ratio.

Are you referring to houses with a given air permeability level there, or including all houses? I thought part of Ph was that the elimination of air movement was important for comfort... so while the above quote may be true for your house, are we talking all houses?

What leaps out at me from this post is its clarity, which suggests you have a clear and thorough understanding of the subject. I think it would make a good primer for anyone wanting to learn about high performance houses, applied to a specific case. Thanks Terry.

My house needs re-rendering and new windows, but only on a subset of the facades. I want to do this "properly". Which means insulating at the same time, installing windows in the correct way, getting proper windows, etc. It also means drawing up a plan for how the house will continue to be improved in the future - "incremental retrofit". From the top of my head I think I will need some professional help to do things like: - Overall aesthetic design - Thermal and moisture modelling - Consider how drainage, services etc are affected by insulation - Help on deciding the best insulant - Ventilation design - Detail drawings for implementing air tightness layer, window installation, closing of cavity etc etc What sort of professional do I need for this?

Just wondering, for full house builds, extensions, extensive renovations... how important do you feel it is that your architect or house designer is locally based, and why? I would define local as being within 30mins or so of site, by whatever means. For a possible upcoming project there are lots of experts I know of, but just one is based within 30mins.

Maybe get a dessicant dehumidifier, if it's cold inside at the moment?

You've said what you're building but not why? What do you want out of the house? Your first two replies were spot on.

What's the purpose of the air conditioning?

I haven't measured it, but I feel the opposite. And surely it depends on the situation. In our house, the cold water tank was almost uninsulated in the loft. There's a clear path for energy to travel from the tank up into that tank. I reckon there'd be loads of heat loss from that. More pipework means more heat loss.

There's no market pressure because the public is uneducated when it comes to air permeability. The normal fallback, regulation, isn't strong enough to make them do it properly. Regulation is bad remember?

Not from what I've heard. The issue is the mechanism cannot take the weight over the long term and inevitably deflects.