Cavity wall insulation advice

[katmark]

Hi all,

I am thinking of having Cavity wall insulation done & was wondering what I need to look out for in terms of material & how it's done. I'll probably use one of the subsidised schemes from British Gas or the local Energy Efficiency council.

I live in a 1960's built bungalow, with wooden suspended floors throughout. The two front rooms (big bay windows) are very cold at the moment, hence considering the insulation (rad in living room is almost 2x BTUs it should be & it's still cold !!).

There is a bit of a problem with condensation/mould in some rooms already - will the walls be warmer with insulation and therefore less condensation on them ?

Any advice would be appreciated.

Thanks

Mark

 

[In Your Face]

Hi, You more than likely have cavity walls possibly without insulation, have you confirmed this? Also do you have any external ground higher than DPC course? Do you have sufficient ventilation? Is your guttering leaking anywhere?

Uninsulated cavity walls can be pumped with insulation. If you can warm up your walls with isulation, heat and keep them dry with a good roof & guttering along with good ventilation this will reduce the condensation and mould.

 

[anobium]

I hate to say it but there is every possibilty that you will end up with more visible condensation if you have cavity wall insulation.
At the moment the excess moisture is condensing on the walls because they are cold.
Filling the cavities will increase the surface temperature of the walls and therefore the excess moisture will then condense on the next coldest surfaces, ie the windows.
Don't get me wrong , cavity wall insulation will reduce the heat loss of your house but, be prepared to have to deal with the condensation problem as a seperate issue, ie dehumidifier or ventilation.

 

[katmark]

Thanks Guys,

there's no insulation in cavity at all (I had a couple of window ledges off last year and saw into cavity - there are metal wall ties though). Bungalow has a concrete 'skirt' around the bottom & no ground is higher than this. Gutters are just cleaned out & are OK & render is fine as well.

I'm a bit concerned about the ventilation to under the suspended floors - should an installer put some kind of ducting in from the airbricks to under the floor ? Will this be OK ? Anything to look out for on this ? (I'll take day off work to make sure all is done OK !)

I thought I'd end up with more condensation, but if it's limited to the cold windows, I think we can live with that.

Thanks again
Mark

 

[memor maplin]

condensation

can be avoided by good ventilation.

Keep the doors to the kitchen and bathroom closed.

Are you drying clothes and moisture is escaping to the rest of the house?

 

[katmark]

Guilty as charged on the clothes dring I'm afraid !

Does anyone have any advice on the best material to use and the issue of ventilation under the supended floors ?

Thanks
Mark

 

[FrankandEarl]

The lower airbricks should already face under the floors ... all the installer has to ensure is that they don't block them up with the pumped insulation gunge.

New fits of double-glazing these days have to come with trickle vents - because new builds are so "tight" against air-flow/humidity correction. Settlement of condensation is a complex and growing problem.

As others said - make sure you haven't got bad gutters/leaks/downpipes etc.

Bungalow has a concrete 'skirt' around the bottom

Do you mean it has 25cm of render around the bottom? These can be a source of bridging your DPC, btw. They are OK when they're sound, not when they're not.

 

[JohnD]

Guilty as charged on the clothes drying I'm afraid

then your home will always be damp and you may as well get used to it unless you change your ways.

Invest in a washing line, or if you can afford it, a vented tumble drier.


//www.diynot.com/wiki/building:condensation_in_houses

 

[katmark]

Thanks for all the advice everyone.

I've contacted local 'Energy Efficiency' centre & although the guy I spoke to couldn't answer any technical questions, they are sending someone out to do a survey who can. Cost will be around £170, which seems good.

The 'skirt' around the house appears to be shuttered concrete (render ?), with the top tapered up to the pebble dash. It's about an 1 '' proud of the house. It all seems to be in pretty good condition.
FrankandEarl - do you mean it could be above the DPC, thus giving a moisture above it ?

We are thinking more about spread of moisture through house - drying more in kitchen where extractor fan is on a lot.

Got a great washing line, but I don't think it's stopped raining long enough to dry a thong recently (not one of mine anyway !!). So much for global warming !! I always dry outside when weather allows.

I'll check out the link as well.

Thanks again guys

mark