Thermal imaging gives the thumbs up!

For the last few weeks, I've been waiting impatiently for cold weather! Why? For the thermal imaging....

When the temperature is cold outside and the house is warm on the inside, any heat escaping through gaps in the building fabric can be seen by a thermal imaging camera. This shows up as hot spots (when viewed from the outside) or as cold spots (when viewed from the inside).

David Hill of Carbon Legacy visited with his thermal imaging camera and we went round the whole house looking for cold spots. We examined window reveals, door reveals and thresholds, wall-roof junctions, and every possible weak point we could think of.

To my huge relief, the results were very good.
- The insulation of walls, floor and roofs is clearly doing its job.
- Junctions between walls and roofs or walls and floors all looked pretty good.
- The window reveals and window sills were my main area of worry, but they were all very respectable too - the worst showed about a 2 degree difference between the cold spot at the corner of the window sill and the adjacent wall, the others were all below 1 degree difference.
- The windows themselves were very good (as you might expect of Green Building Store's triple glazed windows with insulation within the frames and Fakro's quadruple glazed roof-light).
- Where the air tightness work around the front door has not been completed yet, this showed a few cold patches - no surprises there.

Getting such a good result depends on a number of factors, for example: good detailing by the architect (thank you Gil!), the right products (e.g. pro-Clima tapes and membranes), a good builder (McCane Construction), quantity and quality of external wall insulation (Westville using the Permarock system) and the watchful eye of the insulation and air-tightness champion (me).

Of course, the ultimate measure of success for a low energy home is the low energy bill! But first the final bits and pieces have to be completed and then I'll want to see 12 monthly readings for gas and electricity (to compare with the pre-refurbishment readings). However, the signs so far are promising... gas use in December 2012 was a quarter of what it was in December 2010, in spite of the fact that the floor area has increased from 95 to 140 m2.

The gentle art of extreme air tightness

Now that we have a roof, windows and externally insulated walls, it is time to tackle the air tightness to make sure that this low energy refurb really does end up with low energy bills.

For this refurb, the air tightness layer is on the inside: the plaster on the brick walls, tapes around the windows, and a breather membrane across the rafters in the attic.

Today I was most fortunate to have 2 volunteers to help me with taping up the joins in the Intello. (Thank you Debbie and Elaine!)

After a little trial and error, I think I have found a way round some of the more complicated details (with the help of the most flexible type of tape in my tool box).

The moment of truth will be the air tightness test that will follow in a week or two. The preliminary test (before the plastering and the internal tapes and membranes) was respectable - better than the average new build. But once the internal air tightness barrier is in place, we are aiming for a value below 1 ACH at 50 pascals. Will we manage it? Place your bets now....

We have a roof!

The house is starting to look more like a house than a ruin now that it has a roof. The benefits of the insulation on the roof and dormer walls won't be fully appreciated until a few more windows have gone in!

Refurbishments based on passive house principles don't usually have roof lights, but we wanted a bit of extra light in the loft room. However, as roof lights go, the quadruple glazed Fakro rooflight with insulated flashing is probably as well insulated as it is possible to get. The challenge will be to make it completely air tight around the opening, and we plan to add extra insulation around the edge on the inside to minimise cold bridging.

The dormer is the first part of the external insulation work to be completed, and it's looking very smart. It took a bit of coordination and thought to get the vertical insulation to meet the roof insulation all round (battens etc. can potentially get in the way), but we think we've got it well and truly covered!

Loft conversion taking shape

The super-insulated loft conversion is starting to look like a super-insulated loft conversion finally.

It will be a while before the insulation between the joists goes in - but with 100mm of Celotex above the rafters, it feels quite sheltered even without all the windows in yet.

The joins between boards of insulation have been taped on the outside, and will now be filled with foam on the inside to make sure that the insulation is continuous and air tight.

Roof progressing rapidly

All of a sudden the roof seems to be coming on in leaps and bounds - so fast we can hardly keep up!

The roof is now almost weather tight, with Fakro quadruple glazed window being fixed into place and taped up.

The front gable is also wrapped and taped. Be sure to employ a builder who can do origami!

Quite how air tight our very traditional but overly complicated roof structure will be when finished, I'm not sure. My best advice would be - buy a house with a simple up and down roof with gable at each end, or put in for planning to make the roof so! Avoid dormers, overhanging gables over bays, and so on!

The back gable is taking shape too - and we're finding that to be a much easier shape to make air tight and without cold bridges. It might not be that long before we have 180mm of insulation all up the back gable wall to join the insulation above the rafters.

It is looking increasingly unlikely that we'll be close enough to EnerPHit to be worth trying for certification. With the benefit of hindsight, there are various things we could have done some time back to make it easier.