Withington Co-operative Eco-house - spacetherm

The dilemma of building site waste

Robert — Thu, 31 Oct 2013 23:58:54 +0000

Here you're looking at offcuts of Spacetherm which, cumulatively, are equivalent to one full sheet:

Not only does this represent £450 worth of material, the manufacture and transport of it to site is a contribution to the embodied energy of the refurb.

Aside from ordering one less sheet and doing the cutting differently (hindsight is a wonderful thing, as they say!) the question is: can anything be done with this stuff now? Could the manufacturer take it back and give it to other customers? Unlikely, for commercial reasons; Could it be put on eBay or Freecycle? Well, it's a highly specialised product so chances of someone else looking for this at the same time are minimal; Store it for a future project? Possible, but it needs to be stored properly given its handling issues, storage space costs money, and even if I do use Spacetherm again it could well be a different thickness anyway.

So here's the building site waste dilemma: it's a well-known phenomenon that a significant amount of all building materials get thrown in skips without even having been used! I'm sad that my Spacetherm will probably be going the same way... not very 'eco-friendly'!

Progress with internal wall insulating

Robert — Tue, 08 Oct 2013 19:02:18 +0000

The Spacetherming of the front elevation is now complete. Here's how it looks in the upstairs bay, which is now ready for plastering:

Generally speaking, the installation of the Spacetherm by the builders was both slow and error-prone, requiring intervention from myself and Andrew to achieve an acceptable result. As just one example, take the situation where the Spacetherm was intended to slide between the joist and the inner face of the wall, but in practice wouldn't quite fit: the builders' response was to just stop the Spacetherm at the joist:

After being inspected and given more specific instructions, this was amended to sliding a piece of 25mm PIR down behind the joist where the Spacetherm wouldn't go, and taping the PIR and Spacetherm together, above and below:

Today Chris from Back to Earth was on-site giving a tutuorial on installing the UdiReco insulation system. As I wasn't present for most of this, I shall save writing about it until the UdiReco is actually being installed.

Still struggling to get pricing on the Viessmann boiler!

Spacetherm - 1st day

Robert — Wed, 25 Sep 2013 18:44:49 +0000

Here's where the ground floor front room is up to, after the first actual day of Spacetherming:

They've approached in a fairly sensible manner: yesterday they set up a cutting area, and did a couple of tests with small pieces, figuring out the fixing and jointing methods. Turns out that it can be drilled OK (we were advised that drill bits would get snarled up), but getting continuity on the outside angles is really tricky; because there's a built-in VCL behind the plasterboard, any discontinuity of this will create more work afterwards, to get the vapour seal.

Another issue that's cropped up is that due to irregularities in the brickwork and the walls and joists not being quite at right angles, they can't slot the Spacetherm down between the frontmost joist and the wall; some PIR will have to be used instead here, which again is a risk area from a VCL-continuity perxpective.

In other news:

The builders took advantage of the fine weather yesterday to do some snagging on the roof (though still a little more to do there), put the fascia boards on the front
Today they also did one of the knock-outs for the rear patio doors
The plumbing is progressing, but very slowly. I had to resort to ripping out some of the pipework that the "plastic plumber" had fitted, because it was unsatisfactory; needless to say that this didn't go down well! I've resorted to installing the rainwater harvesting system myself now - managing someone else into doing quite literally would take longer than doing the job myself - whilst leaving him to do more "normal" plumbing like radiators
I also had a very positive conversation with a Viesmann installer regarding a replacement for the now effectively abandoned Baxi Ecogen; awaiting costings etc from him in the next couple of days

Spacetherm internal wall insulation (and a general update)

Robert — Fri, 20 Sep 2013 18:32:11 +0000

A while since the last entry... we've now taken delivery of £4,500-worth of Spacetherm, for internally insulating the front wall (see article for a more detailed description). As the delivery was on an 18-tonne truck, we had to decant it into my 3.5-tonne van in order to get as close as possible to the house. The contractors are using their joiner to fit the Spacetherm: a slightly curious choice, but makes sense given that there's some difficult angles around the bay windows, and cutting the stuff neatly will be half the battle.

The walls have been prepared now, and the actual fixing is due to get underway next week.

The plumbing is ongoing, with domestic hot and cold water and most of the waste pipes in now, we're moving on to the rainwater system and radiator circuits next week. Although the on-site work is progressing slowly, the bigger difficulty is that I've had to pretty much abandon the original idea of using a Baxi Ecogen MicroCHP unit in conjunction with a thermal store/buffer vessel. Although it's great in theory, the reality is that Baxi don't have a wide enough installer network for a one-off installation like ours to be achieved cost-effectively. So I am, reluctantly, looking at a condensing boiler system instead - will write more on this next week.

The plaster is pretty much dried out; the builders have fitted the new lintel over the front door, and the new kitchen door was delivered today; will be fitted next week.

United Utilities have promised us that they will be gone from outside the house by 2 October. Fingers crossed!

Design approach: wall insulation

Robert — Fri, 20 Sep 2013 17:57:24 +0000

Retro-fitting insulation to the walls of an existing building is a tricky subject, with much of the theory yet to be substantiated by real-world experience. However, the general consensus seems to be that external wall insulation (EWI) is the preferred option. The key issue is the movement of moisture within the building fabric. For EWI, as long as the insulation material itself is vapour-permeable enough, any moisture within the wall will find its way to the outside. And the original wall will now be on the warm side of the insulation, making condensation less likely (air holds more moisture, the warmer it is). Whilst not without its detailing challenges (window cills, drainpipes, etc), EWI is easier to fit in such a way that it forms a complete thermal envelope around the existing building fabric, with no gaps.

But given the brief of preserving the original appearance of the building, at least as viewed from the street, we opted for internal insulation on the front elevation, and (mostly) external wall insulation to the rear.

For internal wall insulation (IWI), whilst the jury is still out on the appropriateness of a vapour-open approach in some circumstances, installing a vapour control layer (usually a vapour-impermeable membrane) seems to be the safer option when the thermal performance of the wall is unknown. This article explains the use of vapour control layer in internal wall insulation well.

Then there is the difficulty of completing the thermal envelope within floor voids (necessitating taking up/cutting back floor boards, and possibly cutting out joist ends and re-siting them onto joist hangers, so that the timber is not protruding into the cold side of the insulation, where they are at increased risk of decay). Fortunately for us, almost all the floor joists run left-to-right between the party walls, and cutting back floorboards and re-hanging a few joists is not significant extra work as part of a whole house refurb.

"Super-thin" internal insulation

Three of the rooms we are internally insulating have decorative plaster cornices, which are a key feature of the building and thus need to be retained. The original plan with these was to use a "super thin" insulating material up to the underside of the cornice, leaving the latter in situ, and accepting the cold bridge. But one of the cornices got damaged when we had to replace a rotten lintel, and we found a specialist plasterwork company that offered us a special deal price for renewing all three.

We still need super-thin insulation for two rooms that have bay windows though, otherwise the depth of the reveal created would have a detrimental effect on natural light (and these rooms face north, too). We investigated these two alternatives:

Nanopore VIP - Has the advantages of lower cost, increased performance, and no H&S issues. Nanopore (the manufacturer) were helpful, but are fairly new in the UK and couldn't provide a proven fixing method for IWI. We eventually came up with parge-coating the wall with a lime render (downside: 2-3 weeks for it to harden), then sticking the panels on with an adhesive, followed by taping and then plasterboarding. But Nanopore couldn't guarantee that the panels could cope with the weight of the plasterboard and plaster; and any fixing method using battens creates significant cold bridging.
Spacetherm aerogel - More expensive, not quite as thin as VIP for regs-compliant U-values, need to use PPE when installing and set up a well-ventilated cutting area. But has been used elsewhere for IWI. Manufacturer's recommended fixing method is using a nail gun directly into the brickwork. Spacetherm product is aerogel glued to a plywood sheet for strength, a VCL membrane, and plasterboard. We will be using Proclima tapes to seal the joints and edges. The overall thickness is 50mm.

After discussing the different approaches with our contractors and weighing up the uncertainty of the Nanopore option, we decided to go for Spacetherm, despite its extra cost.

"Normal" internal insulation

Given the high cost of Spacetherm, we chose an alternative for the rooms that have just a single, flat, wall - a variant of the UdiReco system chosen for the rear wall EWI. The insulation itself is wood-fibre-based panels, which are screw-fixed to the brickwork. The manufacturer supplies a vapour impermeable render to be applied instead of regular plaster, which forms the VCL. 120mm is required for regs-compliant U-value, though we will use 180mm.

External wall insulation

The system chosen for the rear elevation EWI is UdiReco, a wood-fibre product made by German manufacturer Unger-Diffutherm, and sold in the UK by distributor Back to Earth - who have been helpful and patient throughout this project. Although not the cheapest solution, it has good credentials in terms of vapour control, embodied energy, case studies (they've been using this stuff in Germany for years), and recyclability. The reference for our project was Charlie Baker's house in Chorlton.

These are the key elements of the EWI design:

Udi Reco 180mm thickness to main building rear elevation and return wall of outrigger.
Rafters extended and eaves detailed accordingly.
Render colour-matched to original bricks (deep red/terracota).
New windows to rear elevation installed flush with the external face of brickwork; this means the reveal depth of 180mm + render approximates to the reveal originally, when the windows were installed on the inner leaf of brickwork.
No rainwater or soil pipes on these walls (rear soil stack is internal; rainwater downpipe fixed to outrigger rear wall, which is internally insulated). Unfortunately some penetrations are unavoidable: boiler flue and MVHR terminals (3 of in total).
The original stone cills will have been covered over by the UdiReco, so replicas will be fabricated in steel.

Withington Co-operative Eco-house - spacetherm

The dilemma of building site waste

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Progress with internal wall insulating

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Spacetherm - 1st day

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Spacetherm internal wall insulation (and a general update)

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Design approach: wall insulation

"Super-thin" internal insulation

"Normal" internal insulation

External wall insulation

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