Is geothermal a viable option for me?

mr chips

Some noob questions here.  I'd like to be able to stop using oil altogether, but I'm not sure whether geothermal is a viable option without some serious retrofitting of triple glazing etc.  I have the outdoor space and opportunity to install the pipes for a geothermal system as I've to do a fair amount of earth works/ground-clearing soon anyway, but I don't know whether it would work in my house when I have radiators rather than underfloor heating, no triple-glazing etc.

More specifically, I've a 190 sq. m. house that we bought as a new build 11 years ago - it's conventionally built, i.e. block construction with cavity walls that are filled with beads, but has a slightly unconventional shape in that there are a few different floor & ceiling levels. E.g. the entrance hallway is double height, the ceiling in the sunroom is 1.5 x normal height and the ceiling in the living room is 9'6" high rather than the more usual 8'6".  Feels nice and spacious, but of course it means that a certain amount of heat in winter is a bit wasted.

The house is double-glazed all round and the insulation above the ceilings is 18 inches deep, i.e. 6 inches above the joists.  The central heating runs off an oil boiler of the non-condensing kind, with double-panel radiators in each room (two in the bigger rooms), and supplemented by a wood-burning stove in the living room.  When it gets really cold in winter, we probably have the heating running for between 4-5 hours in the evening and 40-50 minutes in the morning, with the thermostats set anywhere between 21-25 degrees.  The floors downstairs are timber/tile fixed to concrete with the relevant adhesives, so underfloor heating isn't an option.

So am I on a hiding to nothing as regards geothermal?  If so, it's time to start researching wood-chip boilers ...

KCross

My gut instinct says no, based on the amount of time you have the oil running for a 190sqm house which suggests you are leaking a lot of heat. That coupled with conventional rads would make for an over-worked geo unit that will burn out ahead of time or at the very least costs a lot to run.

I think you'd need to start with stopping the leakage via better windows, better insulation and making it more airtight and then if the numbers were right after that consider geo.

I'm not a heating expert so maybe the pros will diss my opinion but I do have a GSHP and UFH so I have some idea.

mr chips

Thanks for that, I sort of expected it tbh.  Like I say, the higher-than-average ceiling height in four of the five biggest rooms (a couple of the rooms upstairs are similar) does mean it takes that bit more to make the place feel warm at floor level.  I'll probably look to get an airtightness test done soon enough, but I'm waiting till I get the front door replaced - the house used to be very leaky in terms of being able to feel little drafts around several of the windows etc on a blowy day, and the insulation in the attic used to be less than half as deep as it is now.  I've sorted most things out and the door is the last major thing on the list - it's a single panel of timber which isn't the best at keeping heat in the house, but all these things take money ...

zulutango

Any idea what your BER is? Geothermal really works best with underfloor heating and underfloor heating really works best if you've a thermally efficient house, i.e. it has a high BER rating. See if you can find out the u-values of the windows too. They might be double glazed but that doesn't mean they're particularly good.

mr chips

Thanks for the reply - underfloor definitely isn't an option as it would cost thousands to retrofit.  When changing mortgage provider a while back, I had to have the house assessed for its energy rating but all I can remember right now is that it got an above average score. That was before we got the solar panels, and we would have done better if as well as having swapped out the more conventional bulbs for low-energy ones, I'd replaced all the halogen spotlights with LEDs. I'm pretty sure that was the BER, but I'll have to dig it out to double-check I'm not mixing it up with something else.  No idea of the u-values of the windows though.
The main reason for my query was because I'm getting a fair amount of earth-moving work done soon, and it'd be annoying to subsequently decide on installing a geothermal system and have to dig it all up a second time!  But even if that's not an option, I've already planted out enough trees (mostly willow) that in maybe another 6-7 years I'll be able to start thinking in terms of a wood-chip boiler fuelled substantially by my own timber.  I've already been able to avoid buying firewood for about 5 years, although for the time being that's only for the wood-burning stove, not heating the whole house.

zulutango

Yes, that would have been the BER alright. Geothermal isn't much use with radiators, I'm afraid. The temperature of the water generated is only about 45 - 50 degrees. Radiators require 80 degrees. In theory you can go for low temperature rads but these will be much bigger for the same heat output. Having said that, if you are getting the earth moving work done, maybe lay the pipes anyway if there's no huge cost to doing so, and then you'll give yourself the option of retrofitting an underfloor heating system. In general, though, you are better off reducing the need for heat and making it a thermally efficient home. Windows are your main source of heat loss (even if they are very good ones) so it makes sense to invest in these. The lower the u-value, the better. It'll be costly but makes a lot of sense in the long run. Woodchip heating, if you're providing your own wood, sounds like a very good option. Be mindful that you will need plenty of dry storage space for the chip and 1 - 2 years for it to dry well enough to be useful as a fuel.

mr chips

Yep, I'm well used to cutting timber and stacking it to dry for burning a couple of years down the line.  Obviously I'd have to invest in a wood chipper, or at least pay for the use of one, but hey - so long as the net cost to me is less than the £1000 a year I currently pay for oil then I'm ahead.
Found my certificate - I'm in NI, so it's not called BER but an Energy Performance Certificate, which is why I was a bit uncertain about whether I was on about the same thing.  The rating was only D63, with potential to be D66 (once the spotlights are swapped for LEDs) - apparently the average rating for houses here is D60.  Like I say, that was prior to installing the solar array, but I'm on about heat rather than light so that makes little difference.  That being the case, unless I find over 20k down the back of the sofa to spend on replacing all the windows with triple-glazing or high-performing double-glazine, I'm fooked. :ermm:  Next best thing might be to put in thermal blinds like Duette or similar, or even shutters on the outside ... !