Does anyone know the date at which the use of thick sheets of rigid polystyrene foam (or whatever it's made of) included in the wall cavity during construction, became part of building regs? I ask because our existing bungalow was extended in about 1985, long before we owned it, and I was wondering if the walls of the extension were insulated.
It isn't mandatory to use polyisocyanturate foam even today.
merely that the house walls are insulated.
My house was new in 1987, and it was built with no insulation in the cavities
It took a while for builders (a notoriously conservative bunch) to understand how to install expanded polystyrene sheeting correctly even when it was required. There are plenty of 80's built houses and extensions with ineffective insulation.
example- Neighbours house had a ground floor kitchen extension done in the 80's. When the current owner extended again, up and out he discovered that the 65 mm cavity had 25mm thick sheets of the white stuff inside the cavity but not attached to anything, or even tightly jointed. Just flopping around loose, sitting on the wall ties, allowing air leakage on both sides, so no effective insulation at all.
There was also an inch thick layer under the slab of the extension, but on top of the DPC with the concrete slab poured onto it without a secondary membrane. Result - concrete fines throughout the 'insulation' thereby rendering it useless as an insulant.
You still can use expanded polystyrene under a ground floor slab but I think it needs to be 5 inches thick to reach current regs. I.e about twice the thickness of 'Celotex'
Last cavity wall here 2012 ish, the builders used rockwool batts. What would be appropriate today and how best installed?
No idf it was all those garages converted to habitable rooms would have a problem, as presumably one new wall neeeds to be built. Brian
Have you looked in the house deeds where hopefully plans for the extension would have been added.
Another possibility is your local council's building control dept. Even if the extension didn't need planning permission it would have needed to conform with building regs and should have been inspected so they may still have the report / plans.
Alan
I think to meet todays regs you need a 100mm cavity that is either full-filled with rockwool batts or 50mm celotex that is firmly fixed to the inner leaf with special plastic wheels that slide over the wall ties. All celotex joints to be taped with aluminium tape. The more diligent builders will also use foaming pu adhesive where any joists sit on the inner leaf.
Full-fill rockwool batts needs to be done carefully, ie batts fully bumped up against each other and no messy mortar spillages on top of the batt as the wall is built up. My 1976-built semi was built by utter morons who threw all the snots down inside the cavity. Every wall tie is a huge glob or mortar and the cavity is solid with discarded mortar about three brick courses above the dbc.
A local builder is constructing a new pie shop for one of our butchers, and even though it is a commercial building the outer walls are rockwool full-filled cavity (100mm) with 100mm inner and outer grey aerated block leaves, the outer one will presumably be clad or rendered as well. I think they used 100mm expanded polystyrene under the slab.
Expanded polystyrene and 100mm rockwool batts are, I believe, cheaper than celotex, but you need a greater thickness to achieve the same heat loss.
Hmmm... How on earth does one apply tape down a cavity with 2" spare? Otherwise OK. I have an extension in progress and had been considering SIP construction.
Outside first? I thought the insulation went in against the inside leaf.
On a cavity retro insulation fit (agricultural) I found the single wire stainless ties would cut PIR insulation easily. 50mm thick strips could be pushed down the cavity. What this did to the foil surfaces, I can't imagine.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.