Cavity Wall Insulation

SpartanKiller · 31-05-2021 8:21pm #1

Hi
I got a quote for cavity wall insulation recently. Contractor is recommended foam rather than beads. Says it'll work better because there's some aeroboard in the cavity already.
What do you think?
I thought it was just beads they were filling walls with.
Thanks

MicktheMan · 31-05-2021 8:50pm

Is the foam product certified for use in a partially filled cavity wall?

Markcheese · 31-05-2021 8:55pm

My parents had a similar dilemma a few years back - the rep at the time was pushing beads - make a complete ****e of the job - the beads didn't travel well around the badly fitted aero board in the wall ,gaps every where , especially around the windows -

SpartanKiller · 31-05-2021 9:02pm

MicktheMan wrote: »

Is the foam product certified for use in a partially filled cavity wall?

This I don't know

SpartanKiller · 31-05-2021 9:06pm

Markcheese wrote: »

My parents had a similar dilemma a few years back - the rep at the time was pushing beads - make a complete ****e of the job - the beads didn't travel well around the badly fitted aero board in the wall ,gaps every where , especially around the windows -

How do they know this?

There seems to be a lot of pros and cons for beads and foam according to people, like foam doesn't last, turns to dust, or beads may lead to moisture movement across the cavity...

Calahonda52 · 31-05-2021 9:15pm

Thermal cabers sorts out the crap work.
Pumping a partial cavity IMO, is ....ox

How do you know its aero board?

SpartanKiller · 31-05-2021 9:28pm

Calahonda52 wrote: »

Thermal cabers sorts out the crap work.
Pumping a partial cavity IMO, is ....ox

How do you know its aero board?

There's an opening in the meter board outside

PMBC · 01-06-2021 8:13am

Calahonda52 wrote: »

Thermal cabers sorts out the crap work.

Calahonda52 - what are thermal cabers?

obriebm · 03-06-2021 1:53pm

Hi all,

Rather than start another thread I figured that it might be easier to post my question here.

We are starting our new build in the coming months. Received the BER report this week but I am looking at insulation options.

It will be a masonry cavity wall build. We are thinking of going 150mm full fill cavity to meet the minimum NZEB standards. The BER report suggests 110mm cavity insulation but that only achieves a u-value of 0.18. Using a full fill cavity can reduce this down to 0.13 according to what I have researched online.

I am wondering is there anything additional that can be performed to get above the minimum standards.

Is external wall insulation an option with a full filled cavity. Aware that there may come a point of diminishing returns so it may not be worth the additional cost but I want to make sure the fabric of the building is solid.

Appreciate any feedback or suggestions.

PMBC · 03-06-2021 2:14pm

How dumb of me- thermal cameras:o

MicktheMan · 03-06-2021 2:14pm

obriebm wrote: »

Is external wall insulation an option with a full filled cavity. Aware that there may come a point of diminishing returns so it may not be worth the additional cost but I want to make sure the fabric of the building is solid.

Appreciate any feedback or suggestions.

It is on an existing house but for a new build why not go with block on flat with ewi, i.e. no cavity? That's how I would build if block building new. It simplifies thermal bridging detailing and very little opportunity to feck it up without it being picked up early visually.

Calahonda52 · 03-06-2021 2:33pm

MicktheMan wrote: »

It is on an existing house but for a new build why not go with block on flat with ewi, i.e. no cavity? That's how I would build if block building new. It simplifies thermal bridging detailing and very little opportunity to feck it up without it being picked up early visually.

.
This worth a re-post

We are fixated with cavity walls.
It is very difficult to get right while being built and impossible to check.
The list of issues is endless.
OP , what about insulated foundations

obriebm · 03-06-2021 2:46pm

Calahonda52 wrote: »

.
This worth a re-post

We are fixated with cavity walls.
It is very difficult to get right while being built and impossible to check.
The list of issues is endless.
OP , what about insulated foundations

Thanks for the replies folks.

I hadn't considered EWI solely but I will look into it in more detail. Our engineer suggested cavity wall as standard but I am open to alternatives.

I have been looking at insulated foundations also, have gone out for quote to two of the large companies here. Our engineer is suggesting a traditional raft but nothing is decided definitively as of yet.

Dudda · 03-06-2021 3:25pm

obriebm wrote: »

Thanks for the replies folks.

I hadn't considered EWI solely but I will look into it in more detail. Our engineer suggested cavity wall as standard but I am open to alternatives.

I have been looking at insulated foundations also, have gone out for quote to two of the large companies here. Our engineer is suggesting a traditional raft but nothing is decided definitively as of yet.

You're engineer is suggesting traditional everything by the sounds of it so he can copy and paste the last 10 projects he's worked on.

If at the starting point of a build flick through the houses on this website. https://passivehouseplus.ie/
(I've no relationship to this site)

Some examples: https://passivehouseplus.ie/magazine/new-build/zero-in-inspired-design-offers-route-to-net-zero-energy-living
https://passivehouseplus.ie/magazine/new-build/passive-wexford-bungalow-with-a-hint-of-the-exotic

I'm not saying look at the design, I'm suggesting you look at the wall, floor and roof build ups. The technical parts and construction photos. They show the u-values, build up of materials and other useful details in a clear easy to understand way. Of the two examples above one is externally insulated and the other is a full fill cavity but it's 250mm wide to fit more insulation. Pay attention to how both projects insulate and make the house airtight at the wall roof junctions, around windows, at floors etc.
You're engineer (by the sounds of it) will just give you standard details from all the other jobs he's done and I think if you do research by looking at the various other houses on that site you'll be in a better position to push what you want.

Biker1 · 03-06-2021 6:20pm

MicktheMan wrote: »

It is on an existing house but for a new build why not go with block on flat with ewi, i.e. no cavity? That's how I would build if block building new. It simplifies thermal bridging detailing and very little opportunity to feck it up without it being picked up early visually.

Have to agree with block on flat and EWI plus insulated slab foundation. It would be my first choice. No need for underfloor heating. Domestic hot water, heating and cooling if necessary and ventilation can be achieved with a heat pump and MVHR.

Cavity Wall Insulation

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