Week 1 of the build

We started on site this week after a rapid exit into temporary accommodation following long awaited granting of planning permission. I was determined that we would not delay the project, before the build had even started, by failing to move out in time. We only just made it though!

The construction team got to work with great alacrity and a building that had been our home three days before very quickly became a building site. All of the wooden stud partition walls are gone, as is all the internal plaster work, which practically came off on its own. Also gone are all the ceilings, all electrical cabling and sockets and all the old kitchen and bathroom fittings. One of the builders found someone to take all of the pine flooring, which he is going to de-nail, re-sand and lay for a small new build in the neighbouring county. Given that it was installed second hand in our house, it will now be getting its third use, which is very satisfying. Still, despite the fact that nearly all the existing structure remains, five or more skips have been filled so far, although the skip company will sort all the contents to separate out any recyclable material.

The attached garage, which is going to be replaced by a single storey new build, is also gone, except for its concrete floor, which goes next week, together with all the windows. Next week also sees the end of the road for the hideous concrete chimney, an original feature I'm told: I really can't imagine what possessed the architect or builder who specified it back in 1970.

It is interesting seeing the building reveal its structure. The quality of the original workmanship is no longer hidden. The 70mm of underfloor screed was removed today to allow us to insulate the floor with the minimum of increase in finished floor height. Unfortunately, the ceiling heights are not especially generous and we could not simply add the insulation on top of the existing screed. The original concrete slab is now exposed everywhere and, as expected, it is very rough and uneven and we will need to find a way to create a level, even base to place the insulation onto. As I think I discussed in an earlier post, the floor was one of the hardest-to-treat elements in the design stage. We were not able to design a floor with a U-value of below 0.15W/m2K, not without spending silly money on very exotic forms of insulation. We have managed to compensate for the relatively poor (>0.25W/m2K) floor U-value but it is still essential we get 70 to 80mm of insulation in there to get the building through Passivhaus Certification.

This week, we have been going through the fiddly process of building up an order for the Internorm windows. We must finalise the order in the next 12 days to avoid risking delaying the project. I had promised myself that we would not cut things so fine with the timing of the window order but this is proving quite hard to achieve. I can see how easy it is to delay progress on a build by taking your eyes off the windows.

One of our windows consists of a large, undivided, fixed, north-facing, triple glazed unit. If there are no other constraints, it is apparently possible to get a U-value for the glazing (Ug) of 0.5W/m2K without using very rare and expensive Krypton gas. Because UK building regulations require 6mm glass for (for inner and outer panes?) in windows of greater than 1300mm height (?), rather than the usual 4mm glass, we lose precious mm of Argon-filled space between the panes. This constraint means that the glazing can only get a Ug of 0.6W/m2K if we stick with Argon. The PHPP will come into its own again when I use it to check whether de-rating this window's glazing to 0.6 will affect the building's overall performance significantly. It is worth doing, as adding Krypton into this one window adds a few hundred pounds (£££) to its price.

It has been interesting as the builder works on further rationalising some of our design choices: balancing materials cost (financially and environmentally) with labour costs and simplifying the execution to minimise the risk of error that could create unintended thermal bridging or air tightness issues. We have managed to simplify a couple of the building junction details. As a client, it adds fantastic value to the project to have that second design iteration. However, it is only working because of the excellent communication and mutual respect between builder and architect. The importance of this team working, "common purpose" if you like, between architect, builder and of course client, has been underlined for me again this week.

Interesting post on Green Living Blog at Guardian.co.uk

There is a lot of talk about the importance of using low embodied energy materials in construction. In our project, there is an element of new build, as well as the refurbishment of the existing house. As I have noted previously, we found that it was impractical in this project to use natural, low embodied materials exclusively. In particular, constraints of the existing structure have meant that we are using a lot of Phenolic foam to insulate the floor (on top of the concrete slab) and externally on the walls. In the new build element we are mainly using wood-based structural and insulative materials.

There is an interesting post on the Guardian's Green Living Blog about this. In a study in Scotland, a two bedroomed cottage takes 80 tonnes of CO2e to build, using standard building techniques and materials. If built to building regs energy efficiency levels, this is the equivalent of six years' energy consumption/CO2e emissions living in the cottage. If that cottage were a Passivhaus, and assuming the energy needed to build it was similar to the standard build, it would take 60 years to 'payback' the energy/CO2e. This gives some support to the argument used by natural material proponents that, if you build a very low energy house, the embodied energy in construction becomes proportionately more important in determining the building's lifetime energy consumption. In the post, they have concluded that refurbishing is the best option (compared with either new build or do nothing) because a refurb of the same sized property is only emits 8 tonnes of CO2e.

Here is a quote from the article. The link to the original is here.

"80 tonnes is a lot – equivalent to five brand-new family cars, about six years of living for the average Brit or 24 economy-class trips to Hong Kong from London. But a house may last for a century or more, so the annual carbon cost is much less – and for all the new-build options, the up-front emissions from construction work were paid back by savings from better energy efficiency in 15–20 years.
However, the winning option was to refurbish the old house, because the carbon investment of doing this was just 8 tonnes CO2e, and even the highest-specification newbuild could not catch up this advantage over the 100-year period. Once cost was taken into account, refurbishment became dramatically the most practical and attractive option, too."