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I attended a CPD today on Passivehaus (by Green Building Store) and it got me thinking about whether we should be going down this route with our refurb (or at least EnerPHit): www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=7709
It's a 1930s mid-terrace house with solid brick walls. MVHR ducting will be tough going. Ground floor is half timber, half concrete (with tentative plans to replace with insulated slab). We're going to build a rear ground floor extension and a loft conversion. We're planning to insulate externally to the front and rear but we can't really go too much more than 160 mm thick due to the small eaves depth (we were planning on EPS but we'd presumably need to change to PIR to hit 0.15 u-value or better). The current design also makes use of raised party walls straddling the boundary to maximise space, which will require internal insulation. Existing party walls are uninsulated. The rear of the building faces West South West. (see attached 3D section of proposed)
It looks (at least superficially) easier than our tear-down/refurb/rebuild (on old stone-built farm buildings); But we didn't quite manage it. Still, it's a good target to aim for and I'm fairly happy with our valiant effort. Air tightness is where we fell (slightly) short.
Considering you have the model, can you get a thermal analysis done to see the effect of various approaches? Should be able to help you get the most economic solution.
Shevek, very few have achieved retrofit passiv haus certification. One of the few is here. Well worth a read to see the pitfalls and solutions. http://ecohome.tumblr.com/
Whats the cost to get it to PH relative to close to PH ?
PH is a great goal but there's 100,000 of house out there that need improvement to reach gov. energy consumption targets, what is the most cost effective way. I believe this may be slightly below the PH target.
One things for sure if you dont get the ventalition sorted out ,condensation and damp may well undermine your efforts. ( as I found out this winter far more than I expected , start on your north wall first :) )
This is what the orientation looks like. I originally designed the rear extension to be orientated to the south but the other two I own the property with weren't keen on it.
Its a bit more difficult when you aren't South facing, we did this one http://www.viking-house.co.uk/passive-renovation.html for Olive in 2009 that was West facing, it has performed pretty well. She said "it was the coldest house in Dublin and now its the warmest". If I was back again I would try to Solar Heat it with a solar roof.
Could you change the shape of your extension roof to catch the sun?
I'm not ignoring the "smart" comments above, just biding my time! Poor tony was targeted on another thread for bearing his sole!
I'm sure I could come up with something (hopefully staying within permitted development restrictions). Do you really think it would make that much different toward Passivehaus?
How big will the house and extension be? How many m2 of solar could you fit on the extension roof? I've a Solar Heating calculator, I'll enter the figures for you.
Books 
Oi.
