Non-motoring > Insulation question Miscellaneous
Thread Author: Bobby Replies: 7
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New Tue 28 Jun 22 17:21 
 Insulation question - Bobby
Random question on insulation - our extension was built with block and brick. I remember at the time they used a foil roll insulation as opposed to Kingspan "boards".

The extension part of the house is always colder in winter rather than the main area. I just dug out old photos of before, during and after build and it looks like the foil insulation was installed between the layer of block and the layer of facing brick?

I am thinking that surely can't be right? You would want your insulation to surely be on the internal wall to prevent heat escaping from the room?

Sadly I can't find any specific note of the exact type of insulation that was used?
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New Tue 28 Jun 22 17:45 
 Insulation question - Manatee
I think the usual choice now is the 'board' or mineral wool. How old is it?
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New Tue 28 Jun 22 19:40 
 Insulation question - Bobby
2010
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New Tue 28 Jun 22 20:52 
 Insulation question - Manatee
The maximum U-value for walls has been 0.35 or less since 2002. Compare with 1.7 in 1965, 0.6 in 1985, and 0.45 in 1990. It's now 0.3.

I don't think you would achieve 0.45 with anything than wasn't a reasonable thickness - 30mm+ maybe but that's a guess.

How's the sealing? Have you bunged all the holes up? Windows?

It's normal to put insulation in the cavity btw. The 'normal' cavity has grown a bit, it used to be 2"/50mm but they now use 60mm at least. Kingspan make a 50mm board which gets brick and block under the building regs maximum.

E&OE, I'm not an expert, MD might have more useful comments.
Last edited by: Manatee on Tue 28 Jun 22 at 20:55
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New Wed 29 Jun 22 13:48 
 Insulation question - MD
It's been a while since I built a cavity wall, but the insulation goes tight to the face of the inner skin of (usually) lightweight concrete block, i.e. Thermalite or Celcon and I'm sure other flavours are available. Joint in the insulation boards should be taped with silver reflective tape.

As for spec' it will also depend on what other provision the specification makes for insulation to the floor slab and ceilings etc.

Unless you are 110% sure that you don't have any damp issues I would avoid retro full fill cavity insulation.

Best................MD
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New Wed 29 Jun 22 13:58 
 Insulation question - sherlock47
>>>How's the sealing? Have you bunged all the holes up? Windows?<<<

But since this month you now have to have extra trickle vents installed in new fit replacement double glazed windows - even if they are capable of being opened. Why?
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New Wed 29 Jun 22 15:08 
 Insulation question - Manatee
>> >>>How's the sealing? Have you bunged all the holes up? Windows?<<<
>>
>> But since this month you now have to have extra trickle vents installed in new
>> fit replacement double glazed windows - even if they are capable of being opened. Why?

To ensure good ventilation/air quality. It probably didn't matter when all houses leaked like a sieve. You still need additional ventilation for gas appliances without an external air supply so if you have a gas hob or woodburner using internal air they will want you to knock further holes in your walls.

The chap who did my air leakage test said that the better built developer houses now are typically hitting 5m³/h.m² @ 50 Pa (building standards max is 10) which he thinks is borderline for decent ventilation unless you have MVHR. (they do the tests with window trickle vents closed).

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New Wed 29 Jun 22 19:27 
 Insulation question - bathtub tom
>>You still need additional ventilation for gas appliances without an external air supply so if you >>have a gas hob

When did that apply from?
I had a new gas hob installed earlier this year, SWMBO arranged it. I found out the fitter wasn't gas-safe registered afterwards. Didn't get any sort of certification or any suggestions holes should be made.
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