external insulation wrap VS pumped cavities for running a heat pump

Colinforeal · 11-05-2022 1:57pm #1

Hi, we are getting an air to water heat pump installed in our 1995 bungalow, currently BER C3. In short the question is, is an external insulation wrap necessary for the heat pump, or will pumped cavities be sufficient?

The context: I appreciate the wrap would be the ideal situation and make the HP most efficient. But wondering if anyone has experience owning or installing for a client, a HP that only had cavity wall?

We are going down the one stop shop route right now, and just waiting on the price. We are pretty much doing every other measure (new windows, air tightness, attic insulation, heat pump installed, blocking chimneys etc etc) but not sure if our budget will stretch to the biggest cost which is the external wrap. I'm expecting 10 - 15k at least for this after the grant. (we are awaiting a price with the wrap and without).

Appreciate any insights or comments. Thanks

Biker1 · 11-05-2022 4:06pm

It will be up to the technical assessor to calculate what insulation measures you will need in order to qualify for the grant. If you are going for the deep retrofit then external insulation is the best option.

Colinforeal · 11-05-2022 5:22pm

Thanks for your reply. We qualify for the grand with or without the wrap. As we will have a BER of B2 or better in both instances and an uplift of 100KW as per SEAI requirements.

So its less about trying to get the grants, but more so how less efficient will the heat pump be with only cavity wall insulation?

MicktheMan · 11-05-2022 8:14pm

What is your air tightness target and how will you ventilate?

Colinforeal · 11-05-2022 9:12pm

If I'm honest, I don't know the air tightness target, and leaving that up to the builder. But is there anything there I should be probing/double checking with him?

For ventilation the OneStopShop said we should be fine with natural ventilation rather than mechanical.

Thanks

Colinforeal · 21-05-2022 7:58am

Just bumping this thread to see if anyone might have any further input on this HP/external wrap combo? Thanks

GIMickey · 17-11-2022 5:25pm

https://www.boards.ie/discussion/comment/119092732#Comment_119092732

Hi Colin,

Just wondering what decision you made as i am in a similar scenario to you.

Technical Advisor did his test and said i am heat pump ready however, everyone keeps saying insulate, insulate, insulate.

So im considering the wrap before the heat pump as i cant get an installer until March anyways for the heat pump.

Did you get the heat pump? Did you wrap or do wall cavity?

Colinforeal · 18-11-2022 12:41pm

@GIMickey - im happy to be able to help here as we are not long finished all the work on our house. In the end I wasnt able to find any independent guidance on forums etc., and just had to go with our gut, but also trust our builder (who was great about everything).

In the end we didnt get the external wrap. It was costing a further 17k after grants which we just couldnt stretch to. The heat pump seems to be working very well now with just cavities pumped (in relation to wall insulation) and the house is holding in the heat. So the heat pump is not being over worked and running 24/7 as I feared it could if there was lots of heat loss through the walls.

As you say, its all about insulation and air tightness. We had 300mm attic insulation rolled out on top of our existing 100mm, we then had all new windows and doors, triple glazed munster joinery with airtightness tape around them, the cavities pumped and 2 chimneys blocked up. The house is now very airtight, almost too much and it was probably a miss not putting in a mechanical ventilation system, something we will probably have to visit in a couple of years time.

One thing I would say is, you seem to be planning to do the work in stages which would mean going down the individual grants route. Doing things this way might allow you to spead the inital outlay on works, but you will miss out on a number of grants (which are only available through the deep retrofit "onestopshop" route). Also if you are installing a heat pump, you really need to be taking a whole house approach to things and ensuring everything else (insulation, airtightness, ventilation etc) is set up to work with/for your heat pump, so for that reason i think its best to do all the work together at once. We had a BER assessor come out and do our initial assessment, he then tried to push us down the individual grants route as he can oversee that and make money from it, but if he advises you to go the OneStop Shop route then you need to go to somebody else, so just becareful what your "technical advisor" is advising you, sometimes these people are not always advising what is best for you or your home, but what is in their best interests.

Hope this helps and all the best with your project

GIMickey · 29-11-2022 1:52pm

https://www.boards.ie/discussion/comment/119889265#Comment_119889265

Thanks very much for all this info. The one stop shop seems more likely now. However I already missed the bonus 2k for reaching B2 if I did it with the OSS.

Thanks again

Biker1 · 20-01-2023 9:05am

https://www.boards.ie/discussion/comment/119889265#Comment_119889265

The technical assessor determines the measures required to bring the heat loss indicator to 2 or below and it does not matter to them whether that costs €500 or €50,000, their fee of a few hundred euro doesn't change. Same goes for the BER assessor, they have no other financial interest in the works other than the fee to do the assessment. It is highly unlikely that a BER assessor would want to manage a retrofit in a private capacity unless they are going down the route of becoming a project manager.

Colinforeal · 23-01-2023 4:50pm

@Biker1 in my experience my BER assessor was very much trying to push me down the individual grants route (and keep me away from OneStopShop). He told me "I can sort all the grants out for you". So I'm assuming, like he gets paid for doing the initial BER assessment, he was going to get paid for each grant he processed, although as you say, someone else, most likely a building contractor, will carry out the actual works

Colinforeal · 23-01-2023 4:55pm

Just to update this thread, we have recently received our post works BER cert and have gone from a C3 to an A3 following the works. Overall very successful and we are delighted with the outcome and have a lovely warm house, with instant hot water and low bills (to be seen yet). One thing we would do better (as I think @MicktheMan was alluding to previously on this thread) is to consider air quality and ventilation more. Now our house is a little too airtight and we really could have done with a mechanical ventilation system being installed, but the was never raised by our builder or OneStopShop. Also the much warmer house has created some condensation issues in the attic too which I am navigating at the moment

sydthebeat · 25-01-2023 6:48pm

https://www.boards.ie/discussion/comment/120146855#Comment_120146855

ive no idea why clients would allow a BER assessor to administer their grants for them. its not a difficult process.

Theres also a €50 grant from seai towards the BER process that im sure that BER assessor is pocketing as well.

Ive done technical assessments for onestopshops. A good assessor should be professional enough to be able to describe all available grants, the pros and cons, and allow teh client themselves to make the choice.

teh big advantage of the onestopshop is that window and door grants are available, whereas they are not if you go individual.

Brianboru39 · 06-03-2023 12:04am

Colin,

Could you share rough estimate of works done and associated costs?

Im just about to embark on a similiar journey albeit going from an E rating

Colinforeal · 07-03-2023 11:04am

Hi @Brianboru39

In short we had:

Cavity walls pumped

Attic insulation

Heat pump fitted

New Windows and doors

Air tightness measures

Total cost 67k

We paid 45k

With an seai grant of 22k

Went from C3 to A3

Brianboru39 · 07-03-2023 5:36pm

Colin,

thanks for the reply much appreciated , could you recommend your contractor or did you do individually?

Colinforeal · 08-03-2023 11:24am

No all through one contractor, highly recommend them. I'm in Donegal and it's just a local contractor working north of Letterkenny. If you are in Donegal too I can PM you their details if you like?

Brianboru39 · 08-03-2023 4:46pm

Not in Donegal but would still be interested in PM

they might consider work elsewhere

external insulation wrap VS pumped cavities for running a heat pump

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