Retrofitting heat pump

maynooth_rules · 07-04-2019 7:44am #1

Is this a crazy idea in a 17 year old house. We currently have a BER of C1. We have oil underfloor heating downstairs and rads UK stairs. Our oil boiler is not condenser and is on its last legs so rather than buy a condensing boiler, I thought I'd bite the bullet and go air to water.
How good does the insulation tlned to be to make air to water viable and not break the bank with electricity bills?
What insulation should I be looking at? Other than pumping the walls and the attic I'm a bit clueless on what else to do.

mikeecho · 07-04-2019 7:52am

I'm following this
I have rads up and down, and an oil condensing boiler.

But this air to heat is something I'm also interested in retrofiting in the future.

KCross · 07-04-2019 11:06am

maynooth_rules wrote: »

Is this a crazy idea in a 17 year old house. We currently have a BER of C1. We have oil underfloor heating downstairs and rads UK stairs. Our oil boiler is not condenser and is on its last legs so rather than buy a condensing boiler, I thought I'd bite the bullet and go air to water.
How good does the insulation tlned to be to make air to water viable and not break the bank with electricity bills?
What insulation should I be looking at? Other than pumping the walls and the attic I'm a bit clueless on what else to do.

How much do you spend on oil per year? That will be an indication of whether A2W is a good idea or not.

Regardless, the more insulated and airtight the house is, the better.

Calahonda52 · 07-04-2019 9:44pm

maynooth_rules wrote: »

Is this a crazy idea in a 17 year old house. We currently have a BER of C1. We have oil underfloor heating downstairs and rads UK stairs. Our oil boiler is not condenser and is on its last legs so rather than buy a condensing boiler, I thought I'd bite the bullet and go air to water.
How good does the insulation tlned to be to make air to water viable and not break the bank with electricity bills?
What insulation should I be looking at? Other than pumping the walls and the attic I'm a bit clueless on what else to do.

What is the flow temp for the UFH?
How big is the buffer tank if any?

Heat pumps work best, giving highest COP, when the temp lift is least.
most flow temps on A2W modern installs are 7C above room temp, so if room temp is 20, then flow temp will be 27: the delta T across the flow and return will be about 5 so the average surface temp will be (27+22)/2 = 24.5

One of the issues that this presents is that the rads will not be big enough at these lower temperatures as most old style oil based systems will have rads designed on a flow of 85, return of 75, average 80, room temp 20 giving a delta T of 60.

You then need to figure out how to get hot water: different ideas, including a HW cylinder fed off the buffer tank, but heated to 60/65 with elec: all night rate.

See attached papers: read the excel one first.

mikeecho wrote: »

I'm following this
I have rads up and down, and an oil condensing boiler.

But this air to heat is something I'm also interested in retrofiting in the future.

See above and attached files

rolion · 08-04-2019 10:18am

My understanding of the heat pumps...
You need a good insulated air tight house.
Leave heat off for a while.
Check the temperature of the rooms in relation to outside weather.
Get your desired internal temperature,optimal and desired.

The heat pump will need to "work and cover" that difference of degrees between house and outside.

I could be wrong !??

maynooth_rules · 14-04-2019 8:40am

KCross wrote: »

How much do you spend on oil per year? That will be an indication of whether A2W is a good idea or not.

Regardless, the more insulated and airtight the house is, the better.

We spent 1500 this year. But we have bee quite stingy.... And rarely warm enough. We have a baby coming so next winter will be double that price of oil I'd say.

Johnny K · 14-04-2019 9:04am

I moved from a C1 house to an A2/3 with A2W HP 3 years ago. From my point of view if you retrofit the the HP to my old house I think you would really stuggled to keep the house warm in winter. Heatpump provides much lower level heating and I would guess you would lose heat quicker than it could be replaced unless you had HUGE radiators eevrywhere. My biggest issue at the moment is our ventilation which is in the form old passive hole in wall. The problem being on a cold windy day you might get too much cold air in one room and the heating can't keep up with the loss. We are in the process of retofitting MHRV.

maynooth_rules · 29-05-2019 11:35am

Just wondering if there is anymore help people can give in regards to this. We intend on spending quite a bit on insulation this summer, but obviously we want to be 100% sure on heat pumps before the big outlay of cash

mickdw · 29-05-2019 11:43am

Hybrid oil with heat pump is an option.
I think it's a safer option in anything bar a new build because if the house isn't really up to A rating standard, I fear the esb bills will suffer and heat pump may even struggle to get enough heat in there.
The hybrid will intelligently use oil / heat pump at most suitable times. If house is cold, oil will bring it up quickly and heat pump will maintain it.
I'm currently involved with a holiday home that is going that route as it's covering off renewable requirement too.

KCross · 29-05-2019 12:26pm

maynooth_rules wrote: »

What insulation should I be looking at? Other than pumping the walls and the attic I'm a bit clueless on what else to do.

maynooth_rules wrote: »

Just wondering if there is anymore help people can give in regards to this. We intend on spending quite a bit on insulation this summer, but obviously we want to be 100% sure on heat pumps before the big outlay of cash

A2W will work fine as long as your are airtight and decent insulation.

I'd suggest you proceed with your insulation and get an air tightness test and seal up as best you can. Then assess where you are at with your oil bill for next winter. It might be the case that it is cheaper to stay on oil if you get the air tighness and insulation right.

Do you have decent quality windows or are they draughty?

One other issue is, with air tighness you will need another means of ventilating, which usually means a heat recovery ventilation system. Otherwise you will end up with damp/mould in bathrooms/kitchens as the moisture will have nowhere to go. HRV will add another few grand to your bill.

ercork · 07-06-2019 9:16pm

The SEAI have a grant for retrofitting heat pumps in houses built before 2006. In order to qualify for the grant though you need to get an assessment done on your house which will tell you how suitable it is and how much work needs to be done to bring it up to spec. It might be worth checking that out.

Muahahaha · 09-06-2019 2:12pm

Johnny K wrote: »

We are in the process of retofitting MHRV.

Did you complete this, if so what system and how is it working for you?

Johnny K · 09-06-2019 3:03pm

Completed about 4 weeks now. Working well. Draughts are all gone albeit the benefits should show in the winter. We had a problem with damp in an ensuite and that seems to be better, when showering there is no condensation on the mirror which would have been totally covered before. One other unforseen benefit was the house is much quieter without Street noise from the wall vents.

The system was installed by proair. We were lucky and the bulk of the ducting to the first floor was accessed through existing built in wardrobes which minimized the disruption.

GreeBo · 09-06-2019 6:44pm

There was another thread here lately where people had crazy bills from an a2w heat pump... before any heading was taking place...
300 a year just for the pump or something?

threeball · 09-06-2019 7:16pm

GreeBo wrote: »

There was another thread here lately where people had crazy bills from an a2w heat pump... before any heading was taking place...
300 a year just for the pump or something?

Specific brand of heat pump I believe. Other units using a fraction of energy on standby.

KCross · 09-06-2019 7:41pm

GreeBo wrote: »

There was another thread here lately where people had crazy bills from an a2w heat pump... before any heading was taking place...
300 a year just for the pump or something?

threeball wrote: »

Specific brand of heat pump I believe. Other units using a fraction of energy on standby.

I'd say its a fault with that particular install or it was measured wrong.

There is no way a modern HP that is in stanby mode would consume that amount of energy. All its doing is powering a basic piece of electronics. Its gotta be a fault. Not normal anyway, for sure.

Johnny K · 09-06-2019 7:45pm

threeball wrote:

Specific brand of heat pump I believe. Other units using a fraction of energy on standby.

Something wrong here. Our bill for the year is e1100 for all heating and hot water. 110sqm house always on set to c20 degrees. 2 adults and 2 kids and all washing is dried in the drier! We have some pv panels but minimum install from builder bought new build.

Muahahaha · 10-06-2019 9:06pm

Johnny K wrote: »

Completed about 4 weeks now. Working well. Draughts are all gone albeit the benefits should show in the winter. We had a problem with damp in an ensuite and that seems to be better, when showering there is no condensation on the mirror which would have been totally covered before. One other unforseen benefit was the house is much quieter without Street noise from the wall vents.

The system was installed by proair. We were lucky and the bulk of the ducting to the first floor was accessed through existing built in wardrobes which minimized the disruption.

Good to hear it is working out for you. Yeah as you said there is a matter of luck in a retrofit, in my own case installing ducts throughout the house would have meant a lot of disruption (and extra cost). I will get a ventilation system eventually, looking at some of the non-ducted versions of HRV which are currently expensive but seem to be coming down in price.

hop · 25-09-2019 4:26pm

did you switch to heat pump in the end...just wondering what your experience of it is

Sophir · 26-05-2020 6:18am

Hi guys will I heat pump work in a house 60 years old, dry lined inside with an insulated slabs, double glazed window ? At the moment only have solid fuel heating. Or should I just install the oil? New rads in the house don't feel like changing them.

Calahonda52 · 26-05-2020 8:42am

How airtight is it?
when the rads were replaced what was the delta T used when sizing them?

Kaybaykwah · 26-05-2020 9:14am

All good points on airtightness, first things first for sure. I live in a big 120 yr old wood clad house. We are in Canada where from December to January, it gets down to minus 30 and July, up to 35 like later today even though it is only late May. The heat pump also provides air conditioning in the summer.

We have a hybrid system with an old oil furnace and recent electric boiler. The heat pump starts in cool weather then the electric boiler kicks in and in really cold minus 10 and below the oil heat takes over. Oil and electric boiler heat older radiators. The house has had insulation updated through the years.

Over here, you can't tolerate the slightest chink of daylight in a door or window sill, otherwise your bills are through the roof, and you are miserable.
I might get geothermal in the future and rid the place of the oil furnace, but the numbers need to add up. I only ordered 500 dollars worth of oil last year and let the electric boiler do the work. It ended up not costing that much, because electricity is cheap here in Quebec, half of what it costs in NYC or Boston because we produce a lot of it. Only problem with heat pump air heating is that the air is dry in the sealed house. The heat is ducted in the first and second storey ceilings, and we run small mist humidifiers so the air is more breathable.

Retrofitting heat pump

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