Will my house be suitable for CWI?

LeafGreen

I bought my house a few months ago - it is only 6 years old so I had assumed it would already have filled cavities.

However, after talking to some neighbours, and checking with the housebuilder, my understanding is that it does not!

The information that I have been able to get indicates that it is "thermal block" insulation. However, confusingly, amongst the paperwork there is a "Cavity Wall Insulation" Guarantee from Instafibre.

I have arranged a consultation regarding CWI but that is a couple of weeks away.

Is it possible to say whether my property is going to be suitable for CWI - is it even worth me having the consultation?

macman

Any house built that recently will have cavity wall insulation.

rogerblack

To be strictly accurate, it may not have insulation in cavities designed in for ventilation of the insulation so that the structure does not become damp.
Filling these risks dampness, and will have very limited benefits, if the building is properly constructed according to the regulations of the time.

Richie-from-the-Boro

grahamgoo wrote: »

I bought my house a few months ago - it is only 6 years old so I had assumed it would already have filled cavities.

However, after talking to some neighbours, and checking with the housebuilder, my understanding is that it does not!

The information that I have been able to get indicates that it is "thermal block" insulation. However, confusingly, amongst the paperwork there is a "Cavity Wall Insulation" Guarantee from Instafibre.

I have arranged a consultation regarding CWI but that is a couple of weeks away.

Is it possible to say whether my property is going to be suitable for CWI - is it even worth me having the consultation?

That would be what we used to call RockWool, its bog standard in new builds and been around for about 25 years or more plus, that is a thermal block insulation .. .. now if your "information given indicated 'thermal blocks' which is Thermalite not rockwool .. .. you should be even more overjoyed.

Wanna be satisfied ? - drill through the darbo only and pull a bit of fibre out, do this in three different places, no fibre, no RockWool. REM - fill holes when finished.

oldskoo1

I recently moved into an 8 year old house

Previous owners mentioned cavity is empty as they had the borescope tests done by several people. Not being able to believe this when we had a new kitchen and extractor I had a look in the cavity myself, yep completely empty.

Kitchen fitter said those are thermalite breeze blocks which act as our insulation and the empty cavity allows the house to keep a moving airflow to reduce the chance of damp.

I then realised all internal walls and room divides are also this thermite block.

So it seems this was the strategy of some builders a few years ago.

Personally I wouldn't get it filled if you have this insulating block. You may be able to tell if your room divides are very thick for a new build.

Even the energy saving trust say you could save up to £130 a year or something like that with cwi. That's only a little over a tenner a month, not a huge saving and that's only a theoretical max.

I'm of the opinion that it might be wiser to check loft insulation (which will also be fine in a 6 year old house) and reduce all drafts.

I've reduced my gas bills in this 8 year old house by setting the ch on timed to suit us, turned it down to 12 overnight with a programmable thermostat and set the boiler to 5 out of 6 on the stat, heating pump on 2 and hot water no more than 60c

rogerblack

oldskoo1 wrote: »

Even the energy saving trust say you could save up to £130 a year or something like that with cwi. That's only a little over a tenner a month, not a huge saving and that's only a theoretical max.

The savings for a building that is already insulated to some degree (with block) will be considerably less.

LeafGreen

thanks everyone. I think you might be correct oldskoo1 - the main internal walls (eg hall-lounge and lounge-dining) are about 14cm (5.5") thick. External walls are about 33cm (13").

the point re loft insulation is also a good one. I do now remember the survey flagged that it wasn't up to the latest standards, but I had assumed that there wouldn't have been that much difference with the standards from 6 years ago. Definitely worth looking into topping that up though - I don't store anything up there.

I am now leaning towards leaving the walls as they are. I haven't yet measured the amount of loft insulation but will do so to see if I may qualify for a free top-up (probably not, I would guess!)

Thanks again for your replies.

rogerblack

grahamgoo wrote: »

thanks everyone. I think you might be correct oldskoo1 - the main internal walls (eg hall-lounge and lounge-dining) are about 14cm (5.5") thick. External walls are about 33cm (13").

I believe for such a recently constructed house, getting copies of the plans from the council may be possible.
This will remove all guesswork, and let you see exactly what the walls (should have been) constructed of.

macman

One small pilot hole drilled will tell you all you need to know. 2 minutes work.

oldskoo1

I enquired with my council but in my case they had no records.

I believe most of the money saving in the loft is covered by the first 150-170mm - further minor / negligable savings can be had by topping up but probably only worth it if its free

I honestly think cwi in my house wouldn't make a noticeable difference. I've always been wary of filled cavities in case at some point damp transfers from the outer skin to the inner wall. It's probably unlikely to be fair and a hot topic here; just my personal opinion.

My biggest improvement was pluging drafts.

Might not save any gas at all but comfort wise, well worth it. I'm talking about gaps around doors and in our case between a newly laid floor and the bottom of the skirting sitting on top. Make sure anyone tackling drafts leaves all ventilation on windows and air bricks.

Not sure if the empty cavity helps but in this house we got much less condensation on the windows in the mornings and the vents are open on some. Only a v.small build in the corners. Our old house with wool filled cavities use to have dripping windows even with vents open.