Category Archives: Renovation

week 17 and 18: existing roof extended

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rafter extension

The rafters to the existing pitched roof have been extended now that the concrete gutters have been removed. This will allow the roof to extend sufficiently in front of the external wall insulation. The Intello air barrier membrane beneath the rafters is Tescon taped to the existing timber wall plate to reduce the air leakage out of the cavity head (see drawing in previous post).

rafter insulation

We are also insulating between the rafters to provide insulation continuity between the external wall insulation and the loft insulation. The rigid insulation panels are squeezed tightly between the timbers and extend approx 0.5m above the (future) loft insulation. This means that they should also serve to provide a ventilation channel into the loft. This ventilation is necessary to remove any condensation from the cold loft space, and is often provided via proprietary ventilation channels.

New, matching roof tiles have been sourced. These will soon be fitted along with the new fascia and gutters – to be continued.

week 17 and 18: base render coat

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Extension wall slurry coat  Existing wall slurry coat

The base render, or slurry coat to the existing walls and extension walls has now commenced. As well as providing a smooth substrate for the external wall insulation, this render coat also serves as our primary air barrier, highighted in blue in the section below.

wall section

Working between sub-zero temperatures (before Christmas) and the rain, the rendering is still ongoing, but having done the front of the property, our house is starting to take on a different look…

house metamorphosing

week 17: cavity wall insulation

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CWI injection  CWI Injection at high level

The cavity wall insulation (CWI) has now gone in. Primarily, it will be the external wall insulation that will be providing the heat loss reduction and achieving our U-values of <0.14 W.m².K. However, in order for the external insulation to be effective, we need to fill the cavity as best as possible to minimise/eliminate air currents. Otherwise, warm air entering the cavity will rise out at the cavity head to atmosphere, bypassing the external wall insulation. The picture above right shows the insulation being injected above the ceiling line of the top floor (usually installations stop just above ceiling level). This is in order to reduce air currents all the way to the cavity head.

We have selected Platinum Ecobead as the CWI insulant. These are expanded polystyrene spheres that are injected at high pressure into the cavity – the manufacturer’s claim this totally fills the cavity, which is good. It is also blown with an adhesive, which means that the beads will stay in place, and not slump, when it dries. As we are replacing the windows and sills, a few days after the CWI installation, we get a unique opportunity to look inside the cavity to see how well the Ecobead has filled it. I am impressed!

viwew of cavity at window sill

week 16: concrete gutters removed

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At last! The gutters that have been causing the leaks in our house, via the cavity of the wall (see earlier post), have been removed. These took some grinding – three cuts needed to get them off and flush with the wall (see orange elements in drawing below). The plan now is to extend the rafters such that the roof overhangs the new external wall insulation and so that we can fit a conventional gutter system.

In addition to them having failed, these concrete gutters were one of the most significant thermal bridges in the house. As shown in the drawing below, we are planning to wrap external wall insulation across the top of the roof and link it to the loft insulation layer. This will significantly reduce the thermal bridging from the remaining elements of the concrete gutter system.

week 13: other odd jobs

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The rear windows to the garage and original dining room store have been removed in blocked up. The dining room store was outside of the thermal envelope of the house, completely uninsulated floor, roof and walls – a real cold spot. The final house will not be short of storage space, but we decided that it would be useful to have some utility storage accessed from the garage. This decision also helps with awkward thermal detailing – i.e. we don’t need to incorporate the store within our thermal envelope. That said, and having just noticed on the photo as I am posting this, I realise that we haven’t incorporated the external wall insulation between this block infil and the existing house walls. A thermal bridge to deal with – any ideas? Ruairi?

getting there with the tender

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Having had a few meetings and pricing addendums with our preferred contractor, we are now getting nearer to the project budget. Essentially, we have re-scoped the works so that the contractor will do the extension, but not the fit-out, e.g. kitchen. For the existing house they will do all necessary external works including:

  • External wall insulation
  • Replacement windows
  • Grinding off concrete gutters and replacing all rainwater goods
  • Structural works and interfacing with extension

Continue reading →

out to tender!

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After a lot of final amendments and hard work, Ruairi sent out the tender documentation earlier this week. We decided to go to four builders: two that we discussed as being the right type and having the right sort of experience; one that was recommended by our structural engineer; and one that was local with a good portfolio, but otherwise unknown.  All tenderers completed a pre-tender questionnaire, which isn’t usual for domestic projects. Tenders are due to be returned in four weeks. Continue reading →

heat storage

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The two thermal images above were taken last week. The image on the left was taken at about 8am on the morning after we had the wood burner on. The one on the right was taken 4hrs later, around midday. With the stove cold (as shown by dark blue/black colours), it is quite striking how much heat is stored in the chimney, which is releasing this beneficial heat into the living room. Continue reading →