Oil, Heat Pump or Something Else? Help!!

davegilly

Head is wrecked with heating decisions for a "new build" that I'm in the process of buying and hoping for some advice from anyone who was in a similar position or who knows what they are talking about. 

The new build isn't quite a new build, it was started about 15 years ago and has been progressing slowly over a number of years and builder has decided to sell it. Currently it has plastered outside walls, scudded internal walls, roof, windows, doors and concrete floor with pipes for rads underneath. There is 100mm insulation under the floor also but no other insulation in the house. The house is a bungalow (200m2) with a very large (150m2) attic space which may eventually be used for a cinema/game room and/or additional bedroom plus attic but right now will be unused due to budget.

The house was plumbed/first fixed for an oil boiler with rads. From my limited research, below are the 4 options available to me and I have no idea which to go for.

1. Install condensing oil boiler with weather compensation and radiators. 300L hot water tank. ($)

2. Install ASHP and radiators. 300L hot water tank. ($$)

3. Install ASHP but instead of radiators, mill the floor and install UFH through the house. 300L hot water tank. ($$$)

4. Install A2A heat pump and ducted system throughout the house. 300L hot water tank. ($$$)

1 is the cheapest I believe with 3 & 4 very expensive. Would anyone have any advice on what to do here? Budget is a concern obviously but as I'm only going to do this once I want to go it as right as I possibly can. The intention is to well insulate the house and have it as airtight as possible also (loads of questions on that too, should I insulate/airtight the downstairs ceiling or do the attic space to allow for future living space or do both???)

Anyway, appreciate any advice or info you can give me. Please don't reply with answers like my house is lovely and warm with x. I know it is and I know all of the 4 options above will provide a warm home. What I'm looking for here is some advice on which is the best, most efficient based on likely install and running cost and what you would go for. I'm into saving the planet and all that as well so oil will eventually be replaced by HVO so no need to knock that!!

Really appreciate any help you can give me here and if any questions or I've left anything out let me know.

Latro

Pedantic air-tightness and insulation is your priority, then HRV.

Heating source is secondary issue then.

If I were you I'd probably go with 2x A2A air conditioning units for heating. Probably best value for money.

Further down the line when your budget recovers as much solar as possible.

graememk

As it's a 15 yr old house essentially. Really depends on what's actually behind the plaster. But you could be stuck with what you've got.

Underfloor works really well with heatpumps due to the low flow temperature, and that also has a benefit for oil heating too.

If running radiators, would they be big enough to meet the heat loss from the house?

randombar

https://www.boards.ie/discussion/2058334603/oil-heat-pump-or-something-else-help

I did the milling myself about 4 months ago. Very happy with it so far. Leads to a much more comfortable house.

Also means I can heat the house on the cheap night rate (with A2W) and stays warm for a long time.

Would love to look more into air tightness myself, hoping companies will offer their services to test and upgrade or something.

Tough decisions to make, if it was me I'd concentrate on the stuff that you don't want to do again. UFH, insulation, air tightness. Easy(ish) to swap out a boiler at a later date.

ColemanY2K

https://www.boards.ie/discussion/2058334603/oil-heat-pump-or-something-else-help

Hi Dave.....i've just finished a self-build bungalow, i designed the house myself. here's my tuppence.

first up, get an engineer if you haven't one already. a good engineer will tell you exactly as they see it.

while it started 15 years ago the house will be considered a new build therefore it'll come under the latest building regs (is the planning permission still valid? usually once the commencement notice is given the building works must be completed within a specified time period).

the level of floor insulation is the bare minimum allowed under the current regs for rads. unfortunately it is insufficient for UFH. 100mm of PIR (i hope it is PIR and not polystyrene) = 0.18W/(m²K), it needs to be 0.15W/(m²K) as a bare minimum for UFH. for context 150mm = 0.13W/(m²K), 200mm = 0.10W/(m²K). the law of diminishing returns applies the thicker the insulation, a lot of new builds today have 150mm of insulation under the screed. perhaps digging up the floor and putting down additional insulation is an option however this is messy, would cost several thousand which you may not have a budget for and would be unnecessary if you opt for OFCH and rads. also threshold levels may negate this as an option. besides 100mm is fine its just the bare minimum acceptable. speak to an engineer for further advice.

https://www.kore-system.com/services/low-energy-building/

the external wall. you didn't say how wide the cavity is. i'm surprised they didn't incorporate insulation as they did the blockwork. if there's no insulation in the cavity then the only option is to have it pumped with beads. in addition insulated plasterboard may be needed if the width of the cavity is insufficient to meet a u-value of 0.18W/m²k. again this is the bare minimum required under the regs and again i would strongly recommend speaking to an engineer.

windows and doors. construction started 15 years ago. how old are the windows and doors? again these need to meet minimum requirements in terms of u values.

airtightness. its going to be very hard to do at this stage without going down the deep retrofit route (which is slightly odd on a new build). 15 years ago it was largely unheard of when this house was started. floor to wall junctions, door thresholds, around the perimeter of window and door opes and where walls are chased are some of the biggest culprits when it comes to air leakage. scudding, scratchcoat and a skim finish makes walls airtight. if there's insufficient cavity for insulation to meet u-value requirements then a scratchcoat will still be needed on inside to make the wall airtight before insulated plasterboard is affixed. it is next to impossible to make plasterboard slabs airtight without a scratch coat underneath. air leaks from underneath or above the slab, through opes for sockets etc. etc.

my neighbour built a 180m2 bungalow 20 years ago. 3 years ago he spent 170k on major renovations. filled the cavity with bead, insulated slab inside, new windows and doors, sprayed foamed the attic, new heat pump etc. etc. 2 weeks ago he told me his monthly electricity bill is €300 and that he is thinking of going back to oil. clearly something is not right, perhaps the heat pump (connected to rads) is not configured right or the house is leaking a substantial amount of heat somewhere or perhaps both. the bottom line is to get a good engineer as they will put you right with regards to the building regs and where this building currently stands.

keno-daytrader

https://www.boards.ie/discussion/comment/121728612#Comment_121728612

This is a fantastic post!

Airtightness will be just as crucial as the level of insulation in the house. You did not mention if you have an engineer or builder on board yet? Its crucial to make sure that they are both on board as to the details of insulation, u-values and airtightness.

If I were in your shoes, before you progress any further, I would take the airtightness course that is offered. I did this on our self build, did all the airtightness myself and found it invaluable, as my engineer and builder really weren't concerned about airtightness. And you will find most trades coming into your house will do the bare minimum and get on to the next job. They will bore holes in the walls cover them up and your screwed if you dont check on them every day. I know your in a different situation with works being already completed somewhat but anything you can do now to prevent air leakage will pay big into the future.

Also just on the 100mm floor insulation, can you see the insulation at any wall junctions or at door opes? Can you be confident that its actually there?

slave1

https://www.boards.ie/discussion/comment/121728612#Comment_121728612

Never too late on floor insulation, took up the floors in my 1970s Semi about a decade ago and put in 150mm of insulation to 50mm perimeter insulated plasterboards, immense difference to the downstairs. My heating is 99% mutlifuel stove now and around €400/season. Insulate Insulate Insulate or you'll be forever heating the place

ColemanY2K

https://www.boards.ie/discussion/comment/121729130#Comment_121729130

true but the OP has said budget is a concern. to buy 150mm of PIR insulation alone will cost circa 5k, concrete another 2k + labour and you'll be looking at 10k plus of a bill...and that assumes the OP sticks with rads, UFH would add thousands more.

slave1

Jesus, is that what it is now, was a fraction of that when I got it done, mind I removed the floor and slabbed the walls myself, fair enough so

ColemanY2K

https://www.boards.ie/discussion/comment/121729270#Comment_121729270

i paid €6,074 last July for 170mm (70 sheets of 100mm & 70 sheets of 70mm) of PIR covering 193m2. i shopped around and bought it from the cheapest supplier in munster. the price of insulation had come off the peak by that stage and was dropping, no idea what it would cost today but i'd imagine somewhere close if not lower than that figure. i along with my brother and cousin laid it out saving 2 days of labour.

the way i see it is the capital cost up front may cost a lot however in the long run you can't put a price on comfort... plus there's the extra savings to your energy bills to go along with it.

slave1

I'm actually going using some 50mm sheets shortly on external walls and the ceiling of a bedroom, currently €28 for a sheet

graememk

https://www.boards.ie/discussion/comment/121728612#Comment_121728612

Although when is the house considered complete? It could have ticked that box years ago.

As for myself and my heatpump " learn by doing 😂" my house idle uses 10kWh/day (I have 2 computers running 24/7, a NAS and main pc).

My night rate was 3800kWh for Dec/Jan 😂

But EV changing was about 1100.

Heatpump was 1400 ish. But I'd say half of it possibly was from batteries, and there is a 20% round trip loss on that. Call 1500

Winter is the biggest use on the farm so house and farm can easily suck up the remaining 1200.

A monthly? bill of 300 is unfortunately meaningless especially if there's estimated reads in the mix too. Also indicates that they could be on a level pay too.

Although on the neighbour front. I wouldn't be surprised that the flow temperature is too high. I specifically picked mine to be a R290 heatpump to be able to hit a COP of 3 (A7/W55).

Markcheese

I'd echo what others have said about spending your money on insulation and air-tightness (-but you'll need ventilation, effectively mhrv some kind, )

So that'd leave you with a condenser boiler or air source heat pump ,

You could always use fan assisted radiators instead of underfloor heating,

Basically a small rad chucking out loads of hot air ( or warm in this case ) , you use the existing piping , and what ever heat source suits -

If you spend your money on insulation/air-tightness you'll need less of a heating system anyway -

ColemanY2K

https://www.boards.ie/discussion/comment/121729552#Comment_121729552

its a fairly standard early 2000s bungalow on an acre with no EV's in the drive...he claimed the lights were costing €5/month...not sure if that was just a throwaway remark while moaning about the heat pump. i was going to offer to have a look at the settings but thought best not to knowing the character involved.

graememk

https://www.boards.ie/discussion/comment/121729733#Comment_121729733

Yeah, just smile and wave boys, smile and wave 😂.

Yeah and my 1500 kWh at night rate is €221 but on full day rate would be €450+! (2 months though.

Standard 1980's bungalow.. windows could do with an upgrade/resealed 😂

People do forget about the €1000+ on oil that would have been spend!