Are building inspectors and cavity wall insulation?

donmaico

Are they not aware of the problems associated with it particularly in seaside areas? Seems not , unless they are getting kick backs form the government to push cwi as much as possible.This family i met recently and who live in the same coastal village as me, was instructed by their inspector that they must have this kind of insulation because of the amount of glass fitted on their new extension.It far exceeds the 25% of floor space allowed but the family were aware of the problems , ie bridging between both wall skins lack of ventilation and rusting wall ties, and raised the question only to be told by the inspector that whilst this were the case 20-30 years ago, things have moved on and better materials are now used which dont create those problems.Is he right, or is he just saying it because the family really has no other option other than remove a huge a amount of glass?Its a sun room which opens into the main house.
I am wondering how fussy these inspectors are bearing in mind that i myself am planning to have one built - 8x4 mtrs, flat roof with a 3 mtr wide bifolding door and a roof lantern(no windows).Iam guessing i would be allowed about 8 sq mtrs of glass in total but taking the height of the doors into account it seems things are going to be a bit tight.Anyone got any advice? I really dont want want CWI.

baldelectrician

When I did my extension up here I wasn't made to put cavity wall insulation in, but I still had to comply to the u-value spec

I did this by by keeping the cavity wall there and filling the timber kit with kingspan on the inside. I also had to have kingspan plasterboard.

donmaico

baldelectrician wrote: »

When I did my extension up here I wasn't made to put cavity wall insulation in, but I still had to comply to the u-value spec

I did this by by keeping the cavity wall there and filling the timber kit with kingspan on the inside. I also had to have kingspan plasterboard.

so in my case would that involve removing the current ceiling(probably lathe and plaster as its a chalet bungalow built in the 20s/30s)) that covers my rafters and replace with kingspan insulation and plaster boards? O

baldelectrician

They specify glass wool on the ceiling- I had to use the stuff on the walls of the new extension

Scottish building regs are more sensable- I had cavity wall in the existing part of the house (before I moved in), but I didn't want it on the new bit

I believe the cavity is there for a reason, so bridging it is taking away is a bad idea (in my opinion)

baldelectrician

If you have to improve the insulation of the existing dwelling you could line the external walls with kingspan board.

I have seen this done and it really helps the ol bit of the house
It is particuarly useful with old sandstone houses where there is no cavity to insulate

iamcornholio

donmaico wrote: »

...... but the family were aware of the problems , ie bridging between both wall skins lack of ventilation and rusting wall ties ......

No, it seems that the family are aware of half-truths and misconceptions.

There is nothing wrong with cavity insualtion done properly in suitable walls.

However for your particular issue, if you want greater glass area, then you need to compensate for the additional heat loss/energy use. Wall insulation is one option, insualting other places is another, more efficient heating is another, or even using more efficient glazing. You just need to decide which is more practical and viable

donmaico

baldelectrician wrote: »

If you have to improve the insulation of the existing dwelling you could line the external walls with kingspan board.

I have seen this done and it really helps the ol bit of the house
It is particuarly useful with old sandstone houses where there is no cavity to insulate

Thats a good thought! in any case i want to improve insulation at some point anyway.but in the short term I would prefer to keep within U value limitations regarding my proposed 8x4 sq mtr extension .At a 25% maximum of floor space allowed , I make it 8 sq mtrs of glass.
A 2.99 mtr (w) x 2.09 mtr (h) bifold door would account 6.2491 sq mtrs which leaves me 1.75 for a roof lantern.The only thing i am wondering here is whether a roof lantern would carry the same allowable percentage as a velux given that there is a great deal more glass involved in the former.

donmaico

iamcornholio wrote: »

No, it seems that the family are aware of half-truths and misconceptions.

There is nothing wrong with cavity insualtion done properly in suitable walls.

However for your particular issue, if you want greater glass area, then you need to compensate for the additional heat loss/energy use. Wall insulation is one option, insualting other places is another, more efficient heating is another, or even using more efficient glazing. You just need to decide which is more practical and viable

CWI would be by far the simplest and cheapest option given the grants available, but i worry about the long term effects that would have on my property.My own surveyor warned me against it as did others involved in the building trade and some in here too.I would need some convincing of its viabilty and wther to use mineral or polystyrene beads.
Greater insulation and more efficient boiler is of importance to me anyway regardless of the extension .indeed i shall have a new combi boiler installed just after the extension is finished and i dont want the glass(pilkington k or similar) to exceed the allowable 25%

donmaico

andrew-b wrote: »

Whats the problem? Why complicate things? Just ignore the scaremongering (wait for the damp proof brigade with vested interests to arrive!!) and build a cavity wall and fill it up during build with suitable slab insulation and fill up the existing walls with retrofit insulation and line the loft with 270mm of loft insulation. Bridging of the cavity wall is usually caused by rubble left in the cavity...NOT by modern CWI materials. Not sure there's any proof that CWI can cause premature wall tie failure either....how many cases have you read about it (google ...you'll be lucky to find one!!). The benefits of CWI far outweigh the very very occassional problems that are rarely even due to CWI but underlying faults of the building.

well when you get conflicting pieces of advice, some from supposed experts ( and a building surveyor as far, as the ordinary layman is concerned, is meant to be one), then it does leave one rather unsure of what is best to do.

I will speak to the guy who is about to replace some of my wall ties, for his thoughts.at the very least if i have them all replaced then they should be good for several years regardless of whether i have the walls insulated or not

Gizmosmum_2

I live on the coast, had cavity wall installed 15 years ago - no problems. I also remember many. many, plumbers rubbishing the installation of condensing boilers because they wouldn't work - they're everywhere now and not just because of building regs.

"unless they are getting kick backs form the government to push cwi as much as possible." Donmaico - I haven't met a building control inspector who has taken "kick backs" from anyone yet and I've worked with quite a lot!

I've yet to find a building inspector who doesn't recommend cavity wall insulation. If they've been recommending it for the last 20 years I think you can safely assume that it's ok. Unless you know better of course.

donmaico

Gizmosmum wrote: »

I live on the coast, had cavity wall installed 15 years ago - no problems. I also remember many. many, plumbers rubbishing the installation of condensing boilers because they wouldn't work - they're everywhere now and not just because of building regs.

"unless they are getting kick backs form the government to push cwi as much as possible." Donmaico - I haven't met a building control inspector who has taken "kick backs" from anyone yet and I've worked with quite a lot!

I've yet to find a building inspector who doesn't recommend cavity wall insulation. If they've been recommending it for the last 20 years I think you can safely assume that it's ok. Unless you know better of course.

i dont , mate, which is why I asked the question.I wil take your advice though as you have had installed.It seems that tradesmen are often quite resistant to new ideas although CWI has been around for some years now.Maybe its the early products that gave lot of problems , ie foam , but modern ones are much better.Did you opt for mineral or polystyrene?