Confused about fireplace and cavity wall insulation?

MissTasmanian

We're currently getting cavity wall insulation but we're a bit confused about what the cavity wall company intend to do about the fireplace. I did try and clarify with the company but they brushed me off saying they'll decide on the day they're doing the work; however, they were suggesting they'd use a combustible vent that will run up the side of the house

I don't understand why this is necessary when they usually seem to use just simple air vents in most peoples' homes. We don't even have an open fire but we did say we might want one in the future. At the moment it's just an electric fireplace.

Le_Kirk

Since COMBUSTIBLE means able to catch fire and burn easily, I doubt they would be installing that! If you are talking about an existing house that has cavity walls, then the insulation will be blown into the cavity. If there isn't a cavity, i.e. your chimney stack, there will be no insulation blown in. Most chimney stacks are solid brick - with a hole up the middle for the smoke etc.

DaftyDuck

I suspect they, and possibly you, might be referring to inserting an air brick in the cavity wall as an air feed for a potential open fire in the future. If this is the plan, I'd leave having it done until a fire is actually installed, as you may well not need one for a small fire.

The fireplace will be unaffected by CWI.

Furts

Fireplaces, chimney stacks and CWI can equal immediate danger areas. To give an example, I have Thermobead CWI. This is a common product used in countless homes. It is forbidden to install this near a chimney. There is a potential fire risk, so you need to be certain on what is proposed. Consequently the drilling/injection ceased within a certain distance of my chimney.

Any air bricks also need consideration - many rooms have a gas fire, or gas fire provision, and there is a danger of Carbon Monoxide poisoning if the air brick is damaged by the CWI.

Obtain the name of the CWI product, and the installer, then obtain a copy of the BBA Certificate, or whatever technical guidance, backs up the product. Read this and be 100% certain you understand exactly what you are letting yourself in for. Bear in mind the Daily Telegraph has run numerous articles on the dangers and defects associated with CWI.

Furts

Le_Kirk wrote: »

Since COMBUSTIBLE means able to catch fire and burn easily, I doubt they would be installing that! If you are talking about an existing house that has cavity walls, then the insulation will be blown into the cavity. If there isn't a cavity, i.e. your chimney stack, there will be no insulation blown in. Most chimney stacks are solid brick - with a hole up the middle for the smoke etc.

To expand a little on this, millions of homes built over the last say, thirty, years will have cavity walls around the chimney. Normal building practice to use cavity walls was adopted here.

MissTasmanian

Thanks for all the help and advice

MrBluesky_2

sometimes they exchange air bricks if they are not suitable for their insulation process,they should atleast fit a liner/sleeve in between the interior and exterior grilles.

That prevents the air brick blocking up and insulation falling through the grilles.

If any fossil fuel are burnt they will need correct ventilation,insulation companies should know all about that.

sometimes they bridge the dpc with the insulation material but they also know about that.