Cavity wall insulation v insulated render?

[whatsthenews]

We recently moved into a 70's 60 sq m 2 bed semi bungalow which has cavity walls.
No insulation so we were considering CWI, however apparently we'd have to have trickle vents fitted to all windows, which we don't really want , however we would qualify for it to be done for nothing. We have had it suggested to us that we buy trickle vents and temporarily stick them to the window frames prior to the CWI firm coming to do the survey.
We had 3 windows made smaller, plus 2 of the other windows had pvc cladding below them down to DPC level and there was no outer course of bricks ,so we ripped that off and created a cavity. All the new block work is breezeblock as we couldn't get a good brick match. The plan is to render in the spring so we were thinking of getting some quotes for insulated render.
The room that's really cold (it warms up when the rad's on, but cools down really quickly )is the only room with 2 external walls which is a bedroom facing SW so it gets battered by the wind. One of the external walls in particular feels very cold to the touch, so cold that we've moved the bed over to the other wall.

Any thoughts please?

 

[jj4091]

My thoughts would be that I have heard so many horror stories about badly installed cavity wall insulaton that I would never consider it. If you have room under your eaves to do a decent looking job then external cladding that was rendered would be my choice. I would also recommend K-rend, either plain or etched paterning looks good especially on a single story bungalow.

 

[noseall]

The plan is to render in the spring so we were thinking of getting some quotes for insulated render.

Give it some thought, i.e. make sure that all external alterations (including cables etc) are complete. Look at soffit overhang. Look at window and door detailing (sills etc). Look at external fittings i.e. gas and electric meter boxes, utilities terminals, extractor fans etc.

CWI is the most convenient by a mile.

 

[Diver Fred]

Best job I've seen on a bungalow in your position is EWI - 50mm insulation batts (breathable) with 20/25mm larch facing.

 

[davidparker]

We recently moved into a 70's 60 sq m 2 bed semi bungalow which has cavity walls.
No insulation so we were considering CWI, however apparently we'd have to have trickle vents fitted to all windows, which we don't really want , however we would qualify for it to be done for nothing. We have had it suggested to us that we buy trickle vents and temporarily stick them to the window frames prior to the CWI firm coming to do the survey.
We had 3 windows made smaller, plus 2 of the other windows had pvc cladding below them down to DPC level and there was no outer course of bricks ,so we ripped that off and created a cavity. All the new block work is breezeblock as we couldn't get a good brick match. The plan is to render in the spring so we were thinking of getting some quotes for insulated render.
The room that's really cold (it warms up when the rad's on, but cools down really quickly )is the only room with 2 external walls which is a bedroom facing SW so it gets battered by the wind. One of the external walls in particular feels very cold to the touch, so cold that we've moved the bed over to the other wall.

Any thoughts please?

CWI would definitely help, but if you don’t want trickle vents, insulated render could be a great alternative, especially since you're already planning to render. It’ll add thermal mass and reduce heat loss on that cold bedroom wall.

For the bedroom, also consider:

Thermal wallpaper or insulated plasterboard on the inside.
Heavy curtains or thermal blinds to help retain heat.
Check for draughts around windows/doors and seal them up.
Since it’s free, CWI is tempting, but if you really don’t want vents, external insulation might be the way to go!

 

[noseall]

larch facing

Have a look again in a few years.

 

[Ivor Windybottom]

The people who do have issues with CWI are a very tiny but noisy minority. Most have absolutely no problems with it and save vast amounts on heating and live much more comfortably. We have it in our 1950s walls and also had it in our previous 1930s house. As with most things, those who are annoyed make lots of noise while those who are happy just quietly get on with life.

Trickle vents are an excellent idea. You can usually close them, if yours can't be closed then you could retrospectively swap them for vents that will close. But you'll probably soon appreciate that they actually make little or no practical difference to temperature and do an excellent job. They're used for good reason, they're not a weird conspiracy just to annoy people.

I'd worry that the free air in your cavity could reduce the value of any cladding on the outside. It's probably open at the top so the cavity can't get heated - any air within the cavity that starts to warm will rise up, float out of the loft and probably pull cold air in from elsewhere.

Just get the free installation. If you're not happy with the vents then change them later.

 

[Ivor Windybottom]

"Insulated render" will probably add little or no insulation - you should check the manufacturer's figures for yourself and compare against CWI. It's probably near useless - better than nothing if you have solid walls and can't add cladding to the inside or out. In other words a last resort in the absence of all other better options. But good if used in addition to other insulation.

 

[whatsthenews]

My thoughts would be that I have heard so many horror stories about badly installed cavity wall insulaton that I would never consider it. If you have room under your eaves to do a decent looking job then external cladding that was rendered would be my choice. I would also recommend K-rend, either plain or etched paterning looks good especially on a single story bungalow.

Thanks. Yes, we have the same feelings about CWI, although we're somewhat reassured that all the external walls are dry, pointing in good condition and nothing external breaching the DPC.
In our last house we had the coloured render put over the top of horrible pebble dash that covered the front of the house from above the ground floor windows to below the 1st floor windows and it looked great. Made such a difference to the front of the house which was a 60's detached with the gable front facing. I can't remember the name of the render he used.

 

[whatsthenews]

The people who do have issues with CWI are a very tiny but noisy minority. Most have absolutely no problems with it and save vast amounts on heating and live much more comfortably. We have it in our 1950s walls and also had it in our previous 1930s house. As with most things, those who are annoyed make lots of noise while those who are happy just quietly get on with life.

Trickle vents are an excellent idea. You can usually close them, if yours can't be closed then you could retrospectively swap them for vents that will close. But you'll probably soon appreciate that they actually make little or no practical difference to temperature and do an excellent job. They're used for good reason, they're not a weird conspiracy just to annoy people.

I'd worry that the free air in your cavity could reduce the value of any cladding on the outside. It's probably open at the top so the cavity can't get heated - any air within the cavity that starts to warm will rise up, float out of the loft and probably pull cold air in from elsewhere.

Just get the free installation. If you're not happy with the vents then change them later

I did wonder about external insulation on an uninsulated cavity wall. It's the appearance of trickle vents I dislike as much as the draught. While we were having the worst of the building work done we stayed in a short term rental for a week . It had trickle vents and even with them in the closed position when it was windy you could feel the cold draught when you were standing about a metre away from the window.
We're very capable of preventing condensation and managing moisture in our home without trickle vents. Annoying when things are forced onto others just because some people for whatever reasons never open windows , don't have / use extractors in wet areas , don't put the heating on and dry clothes in the house.
Surely most 60's homes have plenty of air coming from under the floor and under external doors etc. Different story if your living an (allegedly) airtight new build home.

Give it some thought, i.e. make sure that all external alterations (including cables etc) are complete. Look at soffit overhang. Look at window and door detailing (sills etc). Look at external fittings i.e. gas and electric meter boxes, utilities terminals, extractor fans etc.

CWI is the most convenient by a mile.

Yes external work all done now unless we decide to replace the roof ( going to get a roofer to have a look) . Soffits are UPVC and overhang is about 20 cm . Bathroom extractor would have to be changed. What usually happens regarding windows ? As I said , we'll definitely be getting the front and back rendered ( or cladding might be an option ) because all the window openings have been changed and we have blockwork that needs covering.

 

[whatsthenews]

"Insulated render" will probably add little or no insulation - you should check the manufacturer's figures for yourself and compare against CWI. It's probably near useless - better than nothing if you have solid walls and can't add cladding to the inside or out. In other words a last resort in the absence of all other better options. But good if used in addition to other insulation.

what, even 100 mm solid insulation boards with render over the top? Is that because the cavity will remain uninsulated?

 

[whatsthenews]

CWI would definitely help, but if you don’t want trickle vents, insulated render could be a great alternative, especially since you're already planning to render. It’ll add thermal mass and reduce heat loss on that cold bedroom wall.

For the bedroom, also consider:

Thermal wallpaper or insulated plasterboard on the inside.
Heavy curtains or thermal blinds to help retain heat.
Check for draughts around windows/doors and seal them up.
Since it’s free, CWI is tempting, but if you really don’t want vents, external insulation might be the way to go!

I did think about insulated plasterboard , but assume we'd need at least 50 mm of insulation which means we'd have to completely alter the built in ( to an alcove) wardrobe which runs along an internal wall to meet the really cold external wall in question. I'm going to have a look at the wallpaper option. When you walk into the room it feels like that wall is radiating cold . Windows were all replaced 3 years ago and no draughts there. It's quite a small window for the size of the room and certainly smaller than the one in the other bedroom that only has one external wall.
I'm going to get up on the loft and check the loft insulation is as thick over in that corner and possibly add some more insulation. I think we have about 200mm.

 

[whatsthenews]

Best job I've seen on a bungalow in your position is EWI - 50mm insulation batts (breathable) with 20/25mm larch facing.

I do like the larch but the price

 

[Ivor Windybottom]

I do like the larch but the price

You don't see many old wooden buildings. There's a good reason for that, it's not that they weren't built but that they've mostly turned to compost. Nailing planks of wood to buildings is just a current hopefully passing fad.

 

[Ivor Windybottom]

I'd suggest that there's little point in insulating the wall outside of the cavity if you're not insulating the cavity. As the air in the cavity is probably always going to remain cold whatever you do, so you'll get very little or no benefit.

If you have the option to try different companies under whatever grant scheme then you may find that opinions differ. We were told that we needed trickle vents by a previous company that was going to fit a heat pump. They shut down before starting work, the new company hasn't even mentioned them. If they fit them I'll be fine with it though.