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underfloor heating under floorboards - any ideas on the numbers?
Posted: Mon Nov 18, 2024 9:19 pm
by knighty
hi
Wavn't been here in a while, life getting in the way and all that
We've just moved a few weeks back, big old 1930's house, still has some single glazing (origonal leaded windows) and an oil boiler
I'm thinking as much solar as possible, ground source heat pump and batteires too
Cavity is filled with insulation (Those little polystyreen balls) - havn't looked everywhere yet but when I took the bathroom extractor vent out it looked like a nice big cavity so that's good
We've got 7.5acres of land but a bit of it is forest and the rest has a lot of trees - a qucik google earth check shows we have about 3500 square meters which is open plan with no trees, where ground source install would be easy
Don't have any heat loss calculations yet, I'll sort some ASAP
I can crawl under all of the downstairs floors, they're nice hardwood floors so I don't want to take them up
Anyone have any numbers for heat transfer of UFH if I fix pipes+trays to the underside of the floorboards?
I'm juggling a whole lot of plans/ideas and need more numbers to help tie things down
Tempted by exteriour insulation, but it'll be a hell of a big job to do
sorry for duping so much info all at once! (bit excited)
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Mon Nov 18, 2024 9:50 pm
by Stinsy
knighty wrote: ↑Mon Nov 18, 2024 9:19 pm
hi
Wavn't been here in a while, life getting in the way and all that
We've just moved a few weeks back, big old 1930's house, still has some single glazing (origonal leaded windows) and an oil boiler
I'm thinking as much solar as possible, ground source heat pump and batteires too
Cavity is filled with insulation (Those little polystyreen balls) - havn't looked everywhere yet but when I took the bathroom extractor vent out it looked like a nice big cavity so that's good
We've got 7.5acres of land but a bit of it is forest and the rest has a lot of trees - a qucik google earth check shows we have about 3500 square meters which is open plan with no trees, where ground source install would be easy
Don't have any heat loss calculations yet, I'll sort some ASAP
I can crawl under all of the downstairs floors, they're nice hardwood floors so I don't want to take them up
Anyone have any numbers for heat transfer of UFH if I fix pipes+trays to the underside of the floorboards?
I'm juggling a whole lot of plans/ideas and need more numbers to help tie things down
Tempted by exteriour insulation, but it'll be a hell of a big job to do
sorry for duping so much info all at once! (bit excited)
Sounds like a great property! I’d love a bit of land…
Have a look at secondary glassing for those decorative single pane windows.
What is the loft insulation like? That’s the first place to look, if there is less than 300mm of rock wool sling some more up there.
Received wisdom is that ground source doesn’t justify the expense of installation vs air source. Also we are big fans of A2A in these parts. One of these would take the pressure off the design of the UFH.
UFH and hardwood floors do go together you just need to do the calcs, basically so long as the TOG value is less than 1.5 you’re golden. One challenge is that wooden floors can absorb a huge amount of water over the summer then release it when you turn the heating on making the house uncomfortably humid and causing condensation, therefore you need to ensure the hardwood floors are adequately sealed. You can get insulation with heat spreaders and pipe grooves already in it (eg
https://www.theunderfloorheatingstore.c ... ten-system) and this can be installed from below.
Have you considered outbuildings such as garages/workshops as a way to get more solar?
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Mon Nov 18, 2024 10:03 pm
by drjim
uncomfortably humid and causing condensation
Mandatory MVHR thought process needs to be inserted into your mind.
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Mon Nov 18, 2024 10:09 pm
by spread-tee
UFH with a suspended floor basically comes down to one run up and down the room between each joist which should give a decent output provided you can fix and draughtproof the insulation to a good standard between the joists. Tackling that from underneath is almost impossible IMO, how would you cross over the joists for example? It's not something I would be willing to try. Taking up the floor sounds like a big job but it will be a much more accessible task without all the detritus falling in your eyes and up your nose. Done well it will improve the comfort no end. Personally never seen any of the humidity levels Stinsy mentioned, mostly 90 year old wood is as dry as it will ever get.
Desp
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Mon Nov 18, 2024 10:14 pm
by nowty
I've got a suspended timber floor and fitted a small GSHP or more accurately a water source heat pump. I decided to couple the heat pump to my radiators instead of UFH but instead insulated under the suspended floor with 5cm of polystyrene. I have an electrically (in screed) heated floor in the kitchen and after a couple of years I doubled the insulation under there to 10cm, that made a noticeable difference.
Later I added two ASHP's like Stinsy and they are cheaper, typically more efficient and much less faff than a GSHP.
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Tue Nov 19, 2024 1:29 am
by knighty
I'll have to check properly but looking at the estate agent floor plan and doing the maths in my head there's about 180 sqr meters of floor space, seams a shame not to use it.
I thought the consensus was that air source us great untill you hit negative temperatures and then it's pretty rubbish?
Loft insulation is terrible, but id like to board over most of it for access later (maintenance etc.) so I'll try to get a load of electrical/plumbing work done first before it's all blocked in
We're happy to keep radiators too, just trying to be as efficient as possible, don't want high heating bills when we're retired
The heating system is pretty terrible right now, originally there was a coal boiler outside underground heating the house via radiators in a gravity fed system.... we still have the old 3inch copper pipes in use
Oil boiler is in the cellar with 28mm pipe feeding into that 3 inch stuff, there's a big pump but some radiators are single pipe system some are 2 pipe system, the hot water tank isn't piped up properly, its in parallel wirh the boiler, water flows though it backwards bypassing the boiler
There's an receipt here where the old owners were charged £2500 for a new central heating pump... when a standard pump would have worked just as well (even better if it was plumbed up right!)
Please excuse my spelling/formating, I'm on my phone, can't sleep!
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Tue Nov 19, 2024 4:48 am
by Stinsy
knighty wrote: ↑Tue Nov 19, 2024 1:29 am
I'll have to check properly but looking at the estate agent floor plan and doing the maths in my head there's about 180 sqr meters of floor space, seams a shame not to use it.
I thought the consensus was that air source us great untill you hit negative temperatures and then it's pretty rubbish?
Loft insulation is terrible, but id like to board over most of it for access later (maintenance etc.) so I'll try to get a load of electrical/plumbing work done first before it's all blocked in
We're happy to keep radiators too, just trying to be as efficient as possible, don't want high heating bills when we're retired
The heating system is pretty terrible right now, originally there was a coal boiler outside underground heating the house via radiators in a gravity fed system.... we still have the old 3inch copper pipes in use
Oil boiler is in the cellar with 28mm pipe feeding into that 3 inch stuff, there's a big pump but some radiators are single pipe system some are 2 pipe system, the hot water tank isn't piped up properly, its in parallel wirh the boiler, water flows though it backwards bypassing the boiler
There's an receipt here where the old owners were charged £2500 for a new central heating pump... when a standard pump would have worked just as well (even better if it was plumbed up right!)
Please excuse my spelling/formating, I'm on my phone, can't sleep!
I’d go A2A! That 3” pipe needs to come out (it’ll be so full of sludge you could power flush it ‘till the end of time and not clear it!) so you’re looking at re-plumbing from scratch and that just isn’t worth it IMO.
As we speak it is -3℃ outside and my single A2A is heating the whole 5-bed house just fine (just been up to feed the baby). I wouldn’t necessarily recommend a single unit for the whole house but mine works just fine. A SH or two working in conjunction with a couple of A2A units and a WBS would do a very good job indeed.
Just like solar, EVs and a lot of other green tech, there are a lot of lies and misinformation in the press. The exact same models of HP are used in Scandinavia as we use here.
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Tue Nov 19, 2024 6:52 am
by Stinsy
nowty wrote: ↑Mon Nov 18, 2024 10:14 pm
I've got a suspended timber floor and fitted a small GSHP or more accurately a water source heat pump. I decided to couple the heat pump to my radiators instead of UFH but instead insulated under the suspended floor with 5cm of polystyrene. I have an electrically (in screed) heated floor in the kitchen and after a couple of years I doubled the insulation under there to 10cm, that made a noticeable difference.
Later I added two ASHP's like Stinsy and they are cheaper, typically more efficient and much less faff than a GSHP.
How did you increase the thickness of the insulation under your kitchen slab?
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Tue Nov 19, 2024 8:24 am
by AGT
Sounds like a great job
I would plan underground ducts from locations with some kind of plant room/external building as an energy hub.
Keeps all the kit in one place and saves space in the house,makes it easy to alter/without household disruption.
I would plan electrical, data, waste water, DHW, heating as a priority, planning which can be added as funds/projects allow
Dig trenches once and put lots of ducts in!
I use forecourt solutions online for drawpits, basically 900mm cubes that allow ducting to come in and out and pull points for services.
Good luck
Re: underfloor heating under floorboards - any ideas on the numbers?
Posted: Tue Nov 19, 2024 9:12 am
by nowty
Stinsy wrote: ↑Tue Nov 19, 2024 6:52 am
nowty wrote: ↑Mon Nov 18, 2024 10:14 pm
I've got a suspended timber floor and fitted a small GSHP or more accurately a water source heat pump. I decided to couple the heat pump to my radiators instead of UFH but instead insulated under the suspended floor with 5cm of polystyrene. I have an electrically (in screed) heated floor in the kitchen and after a couple of years I doubled the insulation under there to 10cm, that made a noticeable difference.
Later I added two ASHP's like Stinsy and they are cheaper, typically more efficient and much less faff than a GSHP.
How did you increase the thickness of the insulation under your kitchen slab?
The screed is on top of the suspended timber floor.
