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External Insulation vs Pumping

will56

Hi,

We are looking into improving the insulation in our home
Its a detached house with brick and dash on the front and dash on the sides and back
Front of the house is west facing

Construction: Cavity Block on the sides back and upstairs with a cavity on the front behind the brick.

I got a quote at the weekend of €2,200ish to pump the cavity block all the way around.
The guy providing the quote did say that because of the blocks it would only be a 30-40% fill but we would still see some benefit.

Our other option would be to pump the front and external insulation on the back and sides.
No exact quote for this but he gave a rough price of €20k before the grant.

Best option would be to do the internal wall insulation but my wife does not want to go through the work of taking down the internal walls, plastering and redecorating.

The external insulation seems to be past our budget for the moment, but is pumping the walls going to be a waste of money ?

Has anyone any experience of pumped cavity block walls ?

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Dudda

You want to fill any cavities as much as you can before you externally insulate. What happens is you get something called thermal looping where you get air currents behind the external insulation reducing it’s performance. If you fill cavities as much as you can you drastically reduce these air loops and the external insulation works as it should. External insulation is a much better job than internal insulation for a number of reasons (reduces cold bridges, less disruption, doesn’t reduce floor area, allows greater insulation thickness, improves external appearance of house, etc). Personally I’d insulate the cavity as much as you can now and then start saving for the external insulation. When you're ready to externally insulate come back to us for more advice.

will56

Dudda wrote: »

You want to fill any cavities as much as you can before you externally insulate. What happens is you get something called thermal looping where you get air currents behind the external insulation reducing it’s performance. If you fill cavities as much as you can you drastically reduce these air loops and the external insulation works as it should. External insulation is a much better job than internal insulation for a number of reasons (reduces cold bridges, less disruption, doesn’t reduce floor area, allows greater insulation thickness, improves external appearance of house, etc). Personally I’d insulate the cavity as much as you can now and then start saving for the external insulation. When you're ready to externally insulate come back to us for more advice.

So would you think that the €2k or so to pump the blocks would be money well spent ?

Dudda

will56 wrote: »

So would you think that the €2k or so to pump the blocks would be money well spent ?

Yes, but be aware this is the first step of many to improve the thermal performance of your house. It's an improvement not a final solution.

Over the next 10-15 years you'll want to be looking at external insulation next with new triple glazed windows which are pushed out into the insulation envelope, additional insulation to attic and new insulated and airtight attic access hatch, better heating controls and more efficient boiler or ASHP, improve airtightness throughout and get MVHR if you get good enough airtightness test result, etc.

will56

Dudda wrote: »

Yes, but be aware this is the first step of many to improve the thermal performance of your house. It's an improvement not a final solution.

Over the next 10-15 years you'll want to be looking at external insulation next with new triple glazed windows which are pushed out into the insulation envelope, additional insulation to attic and new insulated and airtight attic access hatch, better heating controls and more efficient boiler or ASHP, improve airtightness throughout and get MVHR if you get good enough airtightness test result, etc.

I understand, I'm not taking anything as a job done solution, just want to see some improvement.
We have the extra layer of insulation in the attic, I'm looking at attic door solutions as well at the moment.
We have zoned hearing and TSV radiators

JonathonS

You will be wasting your money trying to insulate by pumping cavity blocks. Make sure you have 400mm in the attic and save the rest towards the cost of external.

(And don't ask the guy who told you he could 30% fill your walls to quote for the external job).

will56

JonathonS wrote: »

(And don't ask the guy who told you he could 30% fill your walls to quote for the external job).

Why ?

BryanF

will56 wrote: »

Why ?

It’s generally excepted the pumping cavity block is a waste of time, as there are so many solid concrete paths around the insulation.

pumping cavity blocks: question the expertise’s of the contractor.

BUT as is often the case on boards.ie we are getting the story second hand, so perhaps the guy explained the issues of pumping cavity blocks.

https://www.build4less.ie/cavity-block-9-440mm-x-215mm-x-215mm.html

will56

BryanF wrote: »

It’s generally excepted the pumping cavity block is a waste of time, as there are so many solid concrete paths around the insulation.

pumping cavity blocks: question the expertise’s of the contractor.

BUT as is often the case on boards.ie we are getting the story second hand, so perhaps the guy explained the issues of pumping cavity blocks.

https://www.build4less.ie/cavity-block-9-440mm-x-215mm-x-215mm.html

He did explain the issue with the blocks including the issue with cold bridges due to the design of the blocks.
I'm very hesitant to get the external insulation done, 1 because of appearance, 2 because of the cost - won't be able to afford it for a few years
.
The pumped blocks while not a perfect job seems like a reasonable spend for an improvement in the insulation but I'm beginning to doubt that.

JonathonS

will56 wrote: »

Why ?

Although cavity blocks look like they have nice big holes through which beads could flow, in reality the holes are largely blocked by snots of concrete as the blocks are laid. So, unless your contractor is planning to fill the individual blocks the chances of a 30-40% fill are non-existent.

On top of this the cold bridging throughout the wall will mean you will get minimal benefit for your money. €2,000 is a lot to pay for something that will never have a payback in lower fuel bills or improved internal environment, hence I would not deal with anyone who was proposing it.

listermint

Dont take it as gospel, but i would try to do both. To get it right its going to cost alot of money. That is why alot of people try to cut corners or half do it.

In order to get the most out of applications they have to be applied in conjunction with each other.

For example if externally insulating and you have a twin leaf cavity construction, accepted practice would be to pump the cavity first and install external insulation second. this results in the removal of 'thermal loop' or cold / warm air to move around inside the cavity defeating the external insulation outside.

A professional expensive retrofit job done to a high standard would involve bringing the External insulation below outside paths to cover the plinth below ground and bringing the external insulation to the top of the block behind the Fascia board to meet any attic insulation. This would insure that you prevent thermal bridging from the path outside into a concrete foundation slab or under floor. Also helping bridge the gap to the attic insulation.

* This would be higher spec thus higher cost. Smaller gains can be achieved with similar principles but avoiding some bits will still result in % loss of heat out of the building.

Its not an exact science but there is sensible guidelines.

A really top job would require replacing windows at the same time and making sure they are brought external to the house to sit out into the insulation in a window box.

LirW

Sorry for hijacking the thread, I'm looking into the same thing at the moment. We live in an 80's end of terrace and it's a cavity block build.
I know very little about insulation but it seems like external is the way to go.
I have seen companies offering the pumping of cavity blocks but after a bit of googling the response was a quite negative one. Does pumping the cavity blocks really do nothing or could it be a temporary measure while saving for the external insulation and new windows?

We're getting the heating in the house done in a week, since the current heating system is barely working and it's horribly cold in here. I'm basically looking for everything that helps insulate the house.

Dardania

LirW wrote: »

Sorry for hijacking the thread, I'm looking into the same thing at the moment. We live in an 80's end of terrace and it's a cavity block build.
I know very little about insulation but it seems like external is the way to go.
I have seen companies offering the pumping of cavity blocks but after a bit of googling the response was a quite negative one. Does pumping the cavity blocks really do nothing or could it be a temporary measure while saving for the external insulation and new windows?

We're getting the heating in the house done in a week, since the current heating system is barely working and it's horribly cold in here. I'm basically looking for everything that helps insulate the house.

You'd be best looking at windows and ventilation after doing the heating.
With the heating, good heating controls can help a great deal with comfort, and preventing you from feeling too wasteful of energy

LirW

We're getting zoned heating controls.
So it would be best not bothering with insulation for now, especially filling the blocks?

BryanF

LirW wrote: »

We're getting zoned heating controls.
So it would be best not bothering with insulation for now, especially filling the blocks?

will56 wrote: »

He did explain the issue with the blocks including the issue with cold bridges due to the design of the blocks.
I'm very hesitant to get the external insulation done, 1 because of appearance, 2 because of the cost - won't be able to afford it for a few years
.
The pumped blocks while not a perfect job seems like a reasonable spend for an improvement in the insulation but I'm beginning to doubt that.

If you can’t afford ewi, fine. I still wouldn’t pump cavity blocks (note this ‘cavity block’ we are not discussing a cavity between two block leads) pumping cavity block will just make surface condensation on the solid concrete areas worse.

LirW

Perfect, that's what I wanted to know because some people say it won't hurt and some are totally against it. I'm not too sure about it myself but will definitely keep saving then for EWI and new windows.

fillum

I was curious to see what the original poster did in regards the insulation. I'm in a similar predicament in that I've gotten a quote for cavity block foam insulation, but am hesitant due to reading some threads/research online.

will56

fillum wrote: »

I was curious to see what the original poster did in regards the insulation. I'm in a similar predicament in that I've gotten a quote for cavity block foam insulation, but am hesitant due to reading some threads/research online.

I've held off doing anything for the moment.
External insulation seems to be the better way to go but we aren't gone on changing the exterior of the house because.
Plus the cost is beyond our means at the moment.

I do plan to get the cavity at the front of the house pumped which should be a help

fillum

will56 wrote: »

I've held off doing anything for the moment.
External insulation seems to be the better way to go but we aren't gone on changing the exterior of the house because.
Plus the cost is beyond our means at the moment.

I do plan to get the cavity at the front of the house pumped which should be a help

Yeah I was considering doing the same, the front of our home is cavity wall. Thanks for the reply