Retrofit best efficient low cost system

Drog79

Hello,

We are looking at retrofitting an old house. Is the below the best use of a small budget and anyone have this or any advice?

Solar tubes for water and Eddi off PV

Solar PV electricity to underfloor electric mats (heat broken so starting all over again)

Heat recovery

Obviously we start with insulation as the best is not to use energy, but after, does this sound workable?

graememk

Electric resistive heating is cheap to install but expensive to run.

And when you have solar, you usually don't need heat.

How deep a retrofit are you thinking?

Drog79

The above with external insulation

Do you mean the insulation and the HRV might be enough without the ufh mats?

slave1

Not saying its the right route but I went insulation in attic, insulation in the cavity, rip up and put in new floors with a foot of insulation then 50mm insulated slabs on internal walls, all along replacing windows for passive standard N facing and best double glazed remainder of the house. This took a long time.

Then PV and now the PV does house load, water, batteries and EVs

Drog79

So I think we've made decision to go with an post airtricity.

We'll be looking for the one stop shop B2 but as low budget as possible. I see earlier threads mentioning inflated pricing on insulation.

Does anyone have any recent experience?

Busman Paddy Lasty

Not of the One Stop Shop but have done works similar to slave1.

+1 for going big on insulation. How old is your house though? Construction method matters such as solid walls or cavity wall, concrete floor or suspended timber. Sounds like you have radiators already, I'd run a mile from electric mat heating if the floor isn't insulated.

Forum experts say Eddi doesn't give financial payback because of feed in tariff. If you have solar tubes you're getting solar hot water anyway. That could save your budget a few hundred quid.

Drog79

So it's a solid single cavity about 1970 with floating floor(no insulation) and broken heating.It's oil and single rads, so ripping it all out and thought electric ufh might be the way ( we are down a road 50m from nearest gas and sewerage).

We're looking at attic, floor insulation, a wrap and mhrv. Is anyone currently doing reliable passive heating as the air comes in?

Then solar tubes for water and PV for electricity. We basically want an electric off grid everything else house.

We are hoping to keep this sub 50k loan plus grants so all comments and feedback welcome.

Busman Paddy Lasty

+1 for external insulation wrap, attic and floor insulation.

I would query mhrv based on budget. Hopefully others can weigh in, if its 10% of budget and standard wall vents will do, put that at bottom of your list maybe.

Also query electric underfloor. You'll get solar PV in spades this time of year precisely when you don't need heating unfortunately. For us, after boiler losses central heating is 15c per kWh of heat but resistive heating would be 40c. Running that UFH on a day rate in winter could put a dent on your bank balance long term, unless you could build up credit by solar feed in tariff payments.

Appreciate the desire to be off grid but unless you are going to move to Nairobi it just ain't happening in Ireland on a reasonable budget.

Was window replacement brought up at all?

Edit: need to double check if gas figure is correct. It is.

graememk

For the electric under floor, what is actually being done? Subfloor, insulation, screed?

randombar

https://www.boards.ie/discussion/comment/120766155#Comment_120766155

If budget was a factor I'd put in ducting for the MHRV for now and maybe buy the unit at a later date. Retrofit mine, a great job in fairness. Bathrooms were always a disaster with the weak extractor fans. Can keep all windows closed in winter and confident there's still fresh air coming in.

Scoopsire

https://www.boards.ie/discussion/comment/120767294#Comment_120767294

@randombar what unit did you go with? Do you mind me asking was it a self install or got company to handle it all?

DC999

https://www.boards.ie/discussion/comment/120765609#Comment_120765609

As others have said here (maybe in other words), a cheap install could be very expensive to run over the life of it.

Heatpumps multiple the energy so 1kW of electricity can generate 2-4 times the heat. So 1kW of electricity can get 2-4kW of heat That’s how the refrigerant works. The multiplier depends on the kit, design and temp outside and in, and is called the ‘COP’.

All other electrical heaters are a 1-1 ratio. 1kW of electricity = 1kW of heat (or very close to it). So an electrical mat might cost less to install, but will cost a lot to run forever more.

And solar output sucks in winter when you need heating. Our poorest day in winter was 28 times lower than our best blue-sky day in summer (when I don’t need electricity for heating). Or 90kW output in December versus ~600kW in May this year (on a 4.9kWp E/W split).

90kW I got in December couldn’t even heat a single electric radiator for the month. It’s not even close. I used a lot of electric rads last winter for the 1st time as a test to see how it worked with solar – badly, but for me I want to reduce our gas usage too so don’t mind overpaying somewhat on electricity.

Not saying don’t look at electric heating that doesn’t use a heatpump but it costs more than inexpensive gas. 

DC999

https://www.boards.ie/discussion/comment/120761646#Comment_120761646

@ELM327 and others looked at off-grid electric all year round and it's cost prohibitive. It's much easier to be close to off-grid for the 6+ months that you've more solar than you can use. And in late autumn, winter, and early spring you can get away with not buying peak rate electricity if you've large batteries (which could be DIY) and a large solar setup.

And with the FIT for solar you sell back to the grid, the credits in summer could be saved to pay for winter usage.

randombar

https://www.boards.ie/discussion/comment/120767365#Comment_120767365

Vent Axia self install into a 2 storey. Wasn't the worst project.

Drog79

Thanks to all, really helpful.What I'm reading is the electric ufh is a pretty bad idea. In ripping out all the oil and rads, we don't want to use gas at all. So how would this work, and How much do we need of each for the below versus where to spend?

Solar tubes for water and PV for electricity.

Insulation- attic, floor, a wrap and mhrv to not loose heat.

Heat pump for winter heat or another system? ( not gas or electric ufh now). Is there anything available for passive heating as the air comes in?

graememk

Costs. I've no idea, it's something that you need to get quotes for unfortunately. Off grid is hard. And really not budget friendly.

Don't write off oil/gas straight away if you looking to keep install costs down(at least initially)

Solar tubes are great for hot water, but generally it's only in the late spring-early autumn, rest of time it can pre heat it..

Possibly easier to go all in on PV on that aspect.

Having a well designed heating system, doesn't have to be UFH either. One designed with a low flow temperature will work well with condensing oil/gas or even a heatpump.

What was the plan with the electric UFH?

As for Hot water, was it just to top up with an immersion if the solar tubes weren't sufficient.

Another option could be air to air heatpump (eg a mini split, with cassettes in each room) added bonus is you have air con!

It's not as efficient as a wet heatpump (rads or ufh) but still better than resistive ufh

Drog79

There's a lot to think about there, thanks.

The oil system is from the 70s hence ripping out. No gas or sewerage so huge connection fees.

We thought the solars would cover a bit of ufh, even winter, but hearing that's not right so now taking the ground to air pump advice into the mhrv?

We'll have immersion to do the last lift after all this temperate heating too. But I'm definitely of the insulate, recover, solar/ passive mindset

Busman Paddy Lasty

Great mindset in fairness. Reduce, Reuse, Recycle.

Have you had any quotes from a One Stop Shop or any indication of prices?

Drog79

No, not yet waiting on callback but in the meantime if anyone can offer their opinion, its about 150 sq m over two floors.

Busman Paddy Lasty

In our case we wanted heat pump, UFH, passive windows, automated wall vents. After reality bit we went gas central heating with large radiators, regular windows, no fancy ventilation just a hole in the wall!

House is crazy warm and is "heat pump ready", if grants improve or costs come down we can go heat pump when we can afford to.

Separte works into two categories: intrusive and not intrusive. Ducting for MHRV is, but installing the MHRV unit in a loft isn't and can be done later once ducting is in place.

UFH work is intrusive, external heat unit isn't, in your case going UFH with a concrete floor and pipes sized for heat pump, but using an oil boiler now will have you heat pump ready. The boiler swap can be done down the line. They'll be outdoors so no messy work. Aluminium rads etc for upstairs for same reason.

Drog79

After a lot of YouTube videos and to ing and fro ing.

Wrap, solar PV and geotherm are where we're at.

I'd love some vertical geotherm cost advice.

ColemanY2K

https://www.boards.ie/discussion/comment/120896827#Comment_120896827

I don't mean to be gloomy but having read the thread it's hard to see how you can achieve all that you want for 50k after grants.

Plumbing alone with a heat pump (let's say ASHP as I have recent experience of that) is going to cost the guts of 20k. Does the house need rewiring? Another 15 to 20k. UFH only works well if the floor is well insulated i.e. 150 to 200mm of PIR. Buying insulation material alone will cost anywhere from 5.5k to 7k depending on the depth, then you have the concrete screed on top, another 4k poured and screeded. mineral wool insulation for the attic at say minimum 200mm will cost at least €1.2k (most able bodied people can fit this themselves - cheapest place to buy it is B&Q). EWI for a two storey house with a floor area of 150m2 will not be cheap but let's say 20k (I could be way out on this one). Windows and doors, probably 15k if you go with a certain window company in north cork, if not add on another 5 or so K. MVHR kit will cost 4k to buy material. 8k will allow you to get in a specialist to supply and fit. Then you have labour costs on top. Those above are just some of the things you will/might need to do and is in no way exhaustive.

I haven't even mentioned airtightness or solar or the fact your not connecting into the sewer at the end of the lane which presumably means your own sewage system, that could possibly require planning.

My point being is with a limited budget my advice would be to focus on making the house comfortable first and foremost. Attic insulation, EWI, windows/doors and the plumbing be it ASHP or another type of heat system. If the budget stretches then UFH, if not rads.

Either way taking into account the budget and allowing grants keeping within 50k will be an almighty challenge.

Sorry to be all doom and gloom but as someone who's a QS and coming close to finishing their own house the cost of construction/renovation is almost always higher than the client expects. I myself managed to overrun the original budget by 10%, mainly down to the crazy inflation we've seen over the past 12 months and... remember it's my job to manage costs.

So in essence I would recommend first and foremost forking out a few k to seek the advice of a QS. I'm not pitching my services by the way, best of luck :)

AndrewJRenko

https://www.boards.ie/discussion/comment/120896827#Comment_120896827

Did you go ahead with Airtricity for the One Stop Shop in the end? I'd love to hear your experiences.