Heat pump and one stop shop

[Pinoy adventure]

If you were home at the time you’d know if it was done, they’d be sealing up all your vents then sealing the front door and using a big blower to try and pressurise the house. It’s not subtle . But if it was the standard SEAI assessment then it would not have been done.

In new builds they even seal up the toilets.

 

[Zenith63]

covering any mirrors.

Well that’s just common courtesy when having vampires over to the house…

 

[AJAM]

1. COP factor, I presume this is the same for everyone but varies according to the temperature outside?

Temp outside will effect the COP on the day but what's relevant for you is the overall COP of the system over the entire year. By far the biggest factor here is not the outside temperature, but the temperature that you run the heatpump at. If you run it at 35C you will get very high COP if you run it at 55 it will not be good.

2. Presuming you had a well insulated, airtight house, I take it that a heat pump would be cheaper to run than a gas boiler once you got the initial temperature in the house to an acceptable level?

It doesn't have to be well insulated or airtight, as long as you can get the COP above ~2.6 the heatpump will be cheaper to run than gas. Of course if the house is well insulated or airtight it costs even less to heat (for either system) but is much easier to heat and low temps (and hence high COP) for the heatpump.

3. Would you expect that it would take much extra work/much extra disruption if, after adding external insulation and new windows and doors, airtightness turned out to be an issue?

In that situation it can only be the floors or roof. But your technical assessor will be able to tell you what needs to be addressed before the heatpump can be installed.

 

[Micks'r]

Temp outside will effect the COP on the day but what's relevant for you is the overall COP of the system over the entire year. By far the biggest factor here is not the outside temperature, but the temperature that you run the heatpump at. If you run it at 35C you will get very high COP if you run it at 55 it will not be good.

It doesn't have to be well insulated or airtight, as long as you can get the COP above ~2.6 the heatpump will be cheaper to run than gas. Of course if the house is well insulated or airtight it costs even less to heat (for either system) but is much easier to heat and low temps (and hence high COP) for the heatpump.

In that situation it can only be the floors or roof. But your technical assessor will be able to tell you what needs to be addressed before the heatpump can be installed.

"It doesn't have to be well insulated or airtight" ... Very poor advice imo.
The heat loss (i.e. the air tightness and insulation level) is key to a heat pump being worth the investment. On one hand you say COP is key yet on the other hand if your heat losses are greater than the heat the pump can supply at a flow temperature of 35C because of poor airtightness / insulation and you need to bump it up to >50C to compensate then your COP will suffer big time.
Also, just because there is external insulation applied doesn't mean that the walls are air tight and shouldn't be considered for improvement.

 

[Zenith63]

In that situation it can only be the floors or roof. But your technical assessor will be able to tell you what needs to be addressed before the heatpump can be installed.

We discussed this a few posts up, but the heat pump technical assessor will tell you virtually nothing about airtightness beyond the basics of attic hatch seals and window seals. They won’t look under skirting to see if the wall meets the floor, look at LED downlighters to see if they’re airtight or little heat chimneys in each room, for gaps behind light fittings, kitchen cabinets etc. You either want a builder who is tuned into that stuff and is aiming for a particular airtightness number or a separate airtightness assessment.

 

[mir2001]

Thanks @Micks'r and @Zenith63 and everyone else who took the time to contribute here - I feel I have a much better understanding of at least the main pitfalls to watch out for. I won't proceed without an airtightness assessment - the house wasn't well built so I wouldn't be surprised to find out that there are gaps under the original skirting. I don't have any downlighters and the fireplace was sealed up so there is that. I do feel it is very irresponsible of the SEAI to allow technical assessments that do not include an airtightness test as standard, especially given how substantial the upgrade costs are. If anyone has any recommendations on that front then I'd be delighted to get them, thanks.

 

[AJAM]

"It doesn't have to be well insulated or airtight" ... Very poor advice imo.

Sorry, I didn't mean it as advice. I definitely agree, that it makes much more sense to upgrade the insulation and airtightness before installing a heatpump. And indeed that is what I am doing. I've insulated walls, floors ceilings, upgraded windows and doors, air sealed the attic and floors as much as possible and am only now considering a heat pump.

I'm just dispelling the myth that heatpumps don't work in old houses. If your radiators are big enough they'll work just fine.

 

[Cameo]

I live in a 2004 built house that has a geothermal heat pump, the house is big at around 3500 so ft.
As pointed out above the technical assessment for the heat pump is not really fit for purpose as it doesn't require an airtightness test, the HLI is just based on default values and takes no account of how well buikt the house is.

Our house is not that airtight so we've big bills. We are working our way through rectifying this, eliminating the ridiculous number of downlighters in the house, installing insulated plasterboard in all roof areas (making sure the guys seal between the boards!), new doors and windows, might get aerogel (thin insulation) installed in all sills, we've beefed up attic insulation where we can hand have membranes where we can. My point is heatpumps are not super cheap if the house is not airtight and airtightness become more important as you improve the insulation I.e. lack of airtightness has a more proportionate impact

The other point with heat pumps based on my experience and our underfloor heating setup is you are heating the house continuously so you are potentially heating more than you would if you just had gas or oil and were using to boost the temperature. I assume heatpumps can be used to heat rads in the same way so usage can be more controlled

Go around the house with a smoke candle putting against window edges, electrical fittings, attic doors, kitchen presses etc on a windy night and you should get an idea of where drafts are coming from,

I am planning on getting an airtightness test done once I've most work done to get an idea of house

finally ber rating on their own are fairly useless imo

 

[AJAM]

Hi Cameo, Good luck with the upgrades!

My point is heatpumps are not super cheap if the house is not airtight and airtightness become more important as you improve the insulation

I'm going to be pedantic Pat here for a second. If you have a big house (3500SqFt) and poor insulation/poor airtightness, it will not be super cheap to heat, no mater what heat source you are using. But as long as your heatpump COP is above ~2.5, a heatpump will be cheaper to run than oil/gas.

To get your COP up, you need to run the heatpump at lower temperatures.
And to effectively heat a large or poorly insulated area at lower temperatures you need big radiators.