At the time I had mine tested you had to get a 10 or below to past the air test is it still the same?
Ground source heating in a new build
- Thread starter KB6930
- Start date
Something like this, think the term you need is a brise soleil:
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Plenty of air flow here to the top floor. We have electric towel rails on timers in the bathrooms which are all on the north side. Our windows are recessed so we get some shading in the summer but we need a pergola over the large patio doors as they let too much heat in.
Our air tightness was about 0.5 (frame company were disappointed) and then we realised that a window was open.
Sounds fantastic, mine was a traditional brick and block built by local trades, the fact I used traditional build methods and standard UPVC windows but triple glazed not double, with just extra attention to detail maybe accounts for my only getting a 1 rather than better, but I was happy and still am.
air movement is all about air temp Differential My house has minimum air temp differential it’s the same temp everywhere because it’s heated evenly everywhere, So that’s likely why I get so little convection air flow, heat only rises if the air above is cooler than the air below, so my guess is that’s why you get convection air flow and I get very little.
But it also shows that maybe I didn't need upstairs UFH if I was prepared to rely on convection heating by leaving all my doors open a lot of the time, or rely on my heat recovery to spread the heat for me. The problem with leaving the doors open for me is my hallway is my escape route in case of fire so doors are supposed to remain closed especially at night the most likely time you get trapped upstairs by fire. Less of a worry in the daytime.
I would not be shocked if your towel radiators heat the bedrooms the bathrooms are linked too by a fair amount in your case, the minimal heating passive houses need and the amount of heat electric towel radiators can give off is massive I can heat my whole house with 5 kw, so even a 1 kw electric towel rail is mega over kill for just one bathroom. Depending how your controlling it it’s likely heating your bedroom as well.
My 300m2 house only uses 20KWHrs of heat a day max the GSHP only runs about 2 hrs a day its a 10 kw one so that’s about 20kwhrs per day plus solar gain plus living cooking etc, but active heating that’s only 66 watts per m2 per day (mine are north facing or have no windows at all, so an average bathrooms likely what 6 m2 max maybe more but an average, that’s only 400 watt hrs per day thats about 25 mins of a 1kw towel rail, so I can see why you maybe could heat upstairs with electric towel radiators. towel Radiators are likley running at 60 degrees plus so could be why you get convection.
One question, do you light a lot of fires, in a double height living spaces ? These create massive amounts of convection heat. If the house design is designed to help its spread with double height ceilings etc then this is a another possible reason your warm upstairs the massive heat differential the fires create, and double height ceilings heated by them are the perfect environment for convection heating upper floors, and why it’s warm upstairs all that fire place heat shoots up to the highest spot it can reach almost Instantly. Even closed wood burners can create a temperature differential of 100 degrees plus very quickly. That heat quickly pools at the highest point it can reach without restriction.
I intended no criticism of your system or house I hope I didn’t do so. I am thinking of designing another, and if I can understand how your benefiting from convection and I am not it may help Me and others with a better designs for there projects, and me not fitting upper floor UFH systems which are not cheap, a better design is alway a better solution than pumps and extra expense if it can be avoided.
I am thinking of an air flow system that allows convection heat from A wood burning stove to heat upper floors quickly but for it to also have manual control so I can cut it off or restrict it to reduce overheating the upper floors.
Maybe a Louvre duct Or some other element to control air flow Between the upper floors and the room the fireplace is fitted.
My fireplace was possibly a second area that I could have made choices, I maybe should have added one with a back boiler and used that to heat the upper floors (if not the double height living space solution) which I can see it easily doing so. Like you have added towel radiators etc I could have also dumped any overheat into my hot water system. Which with a 1000 litres can always take some extra heat in winter time.
Not sure why you are focusing on convection when you have heat recovery? I have ufh downstairs and a stove upstairs but the primary airflow with all windows closed is the heat recovery. If I have the stove on upstairs in the living room, the positive duct in that room gently moves the heat through to the negative duct in the bathroom where it is redistributed around the rest of the house. In overheating conditions I have 3 hopper windows at the front and 3 at the back that open to create cross ventilation that sucks heat out of the building. No need for heated towel rails anywhere as the overall humidity in the building is around 40%. If you have too much heat stratification I would recalibrate the flows in the rooms to compensate ie bring more fresh into the warmest and get it moving to the coldest.
We don't have any fires, no need and would compromise the airtightness. We have mains gas here so went with that.Sounds fantastic, mine was a traditional brick and block built by local trades, the fact I used traditional build methods and standard UPVC windows but triple glazed not double, with just extra attention to detail maybe accounts for my only getting a 1 rather than better, but I was happy and still am.
air movement is all about air temp Differential My house has minimum air temp differential it’s the same temp everywhere because it’s heated evenly everywhere, So that’s likely why I get so little convection air flow, heat only rises if the air above is cooler than the air below, so my guess is that’s why you get convection air flow and I get very little.
But it also shows that maybe I didn't need upstairs UFH if I was prepared to rely on convection heating by leaving all my doors open a lot of the time, or rely on my heat recovery to spread the heat for me. The problem with leaving the doors open for me is my hallway is my escape route in case of fire so doors are supposed to remain closed especially at night the most likely time you get trapped upstairs by fire. Less of a worry in the daytime.
I would not be shocked if your towel radiators heat the bedrooms the bathrooms are linked too by a fair amount in your case, the minimal heating passive houses need and the amount of heat electric towel radiators can give off is massive I can heat my whole house with 5 kw, so even a 1 kw electric towel rail is mega over kill for just one bathroom. Depending how your controlling it it’s likely heating your bedroom as well.
My 300m2 house only uses 20KWHrs of heat a day max the GSHP only runs about 2 hrs a day its a 10 kw one so that’s about 20kwhrs per day plus solar gain plus living cooking etc, but active heating that’s only 66 watts per m2 per day (mine are north facing or have no windows at all, so an average bathrooms likely what 6 m2 max maybe more but an average, that’s only 400 watt hrs per day thats about 25 mins of a 1kw towel rail, so I can see why you maybe could heat upstairs with electric towel radiators. towel Radiators are likley running at 60 degrees plus so could be why you get convection.
One question, do you light a lot of fires, in a double height living spaces ? These create massive amounts of convection heat. If the house design is designed to help its spread with double height ceilings etc then this is a another possible reason your warm upstairs the massive heat differential the fires create, and double height ceilings heated by them are the perfect environment for convection heating upper floors, and why it’s warm upstairs all that fire place heat shoots up to the highest spot it can reach almost Instantly. Even closed wood burners can create a temperature differential of 100 degrees plus very quickly. That heat quickly pools at the highest point it can reach without restriction.
I intended no criticism of your system or house I hope I didn’t do so. I am thinking of designing another, and if I can understand how your benefiting from convection and I am not it may help Me and others with a better designs for there projects, and me not fitting upper floor UFH systems which are not cheap, a better design is alway a better solution than pumps and extra expense if it can be avoided.
I am thinking of an air flow system that allows convection heat from A wood burning stove to heat upper floors quickly but for it to also have manual control so I can cut it off or restrict it to reduce overheating the upper floors.
Maybe a Louvre duct Or some other element to control air flow Between the upper floors and the room the fireplace is fitted.
My fireplace was possibly a second area that I could have made choices, I maybe should have added one with a back boiler and used that to heat the upper floors (if not the double height living space solution) which I can see it easily doing so. Like you have added towel radiators etc I could have also dumped any overheat into my hot water system. Which with a 1000 litres can always take some extra heat in winter time.
Then I see the likely reason for your convection, your heating is a more on off bursts of heat when required rather than a slow release. That I use.
There are plenty of stoves suitable for air tight homes, nowadays they all use external air supples, and can operate completely room sealed.
Also we were 100k over budget so the stove along with many other things got cut. We're not missing the stove though. Water temp is only 30 degrees, air temp is 23 without much help, cuts down to 18 overnight, even in December we were hitting 25 degrees by midday on a sunny day with no heating on after 8am.
That’s how mine works to a point, my stove even with it only being a 5kw and room sealed, can overwhelm the room it’s in, in only 3-4 hrs, even with the rooms doors open and the room being about 75m2 in size. I agree the heat recovery moves the heat, but as all bathrooms are extraction points what tends to happen in my system is they get cool where the house is warm in general.
I to have about 40% humidity and the heat recovery works well with the UFH I use 98% of the time the heating is on at all.
while your system over time moves the air arriving from outside into your living room is then slowly pulled into the extraction points in bathrooms over time, that cannot happen in my system.
where I have the stove, as it has both air intakes and Air extraction points it’s in balance, the only way mine can move is via the heat recovery unit it’s self at the moment, I suppose I could manually block those vents and see what happens as this like your system would cause an imbalance in that large room and force air to move via air flow to other extraction points in my house.
Maybe worth a try
Only 20% of the total air extracted is from that room as I have about 10 extraction points so heat is moved very slowly as you can imagine.
Moving to a imbalanced room system like yours would create far more airflow as 60% of the extraction is in the top 2 floors blocking all my ground floor extraction apart from the bathroom would bump it to 90% my down stairs would become positive air pressure zone and move to the newly negative air pressure upstairs zone upstairs.
so thanks I will Maybe give that a try come November time.
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Budgets are alway tight by that stage, that 100k would have put me 33% over budget, which was never an option, for me. I can see why you cut the stove.
For me the stove is more about having heat if the power goes out, than heating my house day to day.
That’s why it’s not really setup to heat my house fully. And I had zero budget at the time to do it any other way.
If the power went out here we'd put another jumper on. That would be enough. I've never seen the thermometer below 18 after the windows were fitted, and that was in February.Budgets are alway tight by that stage, that 100k would have put me 33% over budget, which was never an option, for me. I can see why you cut the stove.
For me the stove is more about having heat if the power goes out, than heating my house day to day.
That’s why it’s not really setup to heat my house fully. And I had zero budget at the time to do it any other way.
scavinge
Member
- Location
- kent downs
I ve just got my scaffold down, Brick and block with 125mm full fill cavity. Orginal design was for oil boiler now going for ASHP, under floor heating on ground floor, company has suggested first floor radiaitors are not put under the windows. Anyone have experience where the rads work best in the bedrooms, i guess they are on the large/long size for low temp.
Davey
Member
- Location
- Derbyshire
I guess the issue is that a lot of heat may be lost straight out of the window?
Fine if there is somewhere else for it to go but equally the space under the window tends to be relatively useless hence making it the best place to put the radiator
Water Wheel
Member
An interesting thread.
One or two bits of the thread I don’t understand-
Is this an additional summer inlet to the MHRV system or the only air inlet for ventilation , could you explain a bit more, would a summer by pass not be sufficient ? Or perhaps cooling the floor with the heat pump in reverse.
The other topic not cover much is floor covering. With a high thermal mass, constant floor temperature with low water temp. in the UFH, are wood floors ok. My wife would like carpet in sitting room and bedrooms and wood in the very large Kitchen/ dinner/ day room.
I would go for a lot more stone especially in the kitchen / dinner.
We are at the planning application / dreaming stage. My dream is as near passive house as local builders can manage; my wife fights shy of any “new” technology!
The intention is a 225m2 new build bungalow, to replace a small awful 1970s build bungalow, unfortunately bats are this weeks issue even in a 70’s building. Current thoughts are for ground source heat pump for UFH and hot water, and Mechanical Heat Recovery Ventilation with a small sealed log burner as backup. No oil boiler.
Construction to be strip foundation, brick and block cavity wall , floor insulation under concrete slab to give a high thermal mass, with as much attention to airtightness, thermal bridging and insulation as I can manage.
My wife is not entirely on board yet, doesn’t want to live in an airtight box, wants radiators so we can warm house up more quickly when cold etc etc . Yes I know !
One or two bits of the thread I don’t understand-
Is this an additional summer inlet to the MHRV system or the only air inlet for ventilation , could you explain a bit more, would a summer by pass not be sufficient ? Or perhaps cooling the floor with the heat pump in reverse.
The other topic not cover much is floor covering. With a high thermal mass, constant floor temperature with low water temp. in the UFH, are wood floors ok. My wife would like carpet in sitting room and bedrooms and wood in the very large Kitchen/ dinner/ day room.
I would go for a lot more stone especially in the kitchen / dinner.
We are at the planning application / dreaming stage. My dream is as near passive house as local builders can manage; my wife fights shy of any “new” technology!
The intention is a 225m2 new build bungalow, to replace a small awful 1970s build bungalow, unfortunately bats are this weeks issue even in a 70’s building. Current thoughts are for ground source heat pump for UFH and hot water, and Mechanical Heat Recovery Ventilation with a small sealed log burner as backup. No oil boiler.
Construction to be strip foundation, brick and block cavity wall , floor insulation under concrete slab to give a high thermal mass, with as much attention to airtightness, thermal bridging and insulation as I can manage.
My wife is not entirely on board yet, doesn’t want to live in an airtight box, wants radiators so we can warm house up more quickly when cold etc etc . Yes I know !
- Location
- North West Wales
We’ve got tiles throughout apart from lounge which is engineered wood. We’ve never had the floor warm in the lounge (after initiall floor drying ten days process) as we have a log burner there and use it as an excuse to light the fire. I do sometimes turn the stat right up for ten minutes just to circulate the water in that zone. It’s lovely having nice warm tiles on a cold morning though.
Speedstar
Member
- Location
- Scottish Borders
We are on with a new bungalow , ground source heating with under floor heating and solar thermal panels for hot water, floors are tiles in the bathroom, karndean flooring on the rest but you can use carpet or rugs but they need to be the right kind
The inlet is the permanent inlet it’s in use 24/7 365 days a year.
It’s a good system that pulls heat from your underfloor in summer I don’t have it but I I ever have to change my heat pump I would get it. With that and the passive in ground pipe you would keep your house cooler in summer conditions, while it provides you with hot water.
I personally would add solar electric to any new house roof, while not mega attractive in panels there are other options around now that while they come at a cost can do the job nicer.
I also thinK that solar hot water is so cheap that a basic system is easy to do.
air tight while on paper seems like it would be stuffy is far from it and you can always still open a window if you want, you just except that in winter that comes at a great cost.
My house gets its entire volume of air exchanges every 2 hrs that will be far more fresh air than any normal trickle vent in Windows would ever supply. and this is warmed (When not in summer bye pass) And filtered air, via the heat recovery unit.
good luck
Bringing this up again !!!!
We're building a 2 storey timber frame house this year triple glazed windows good insulation under floor heating both floors etc.
I always wanted ground source heating but it's a good chunk more expensive and I think I'd go with a borehole rather than ground collector pipe. Our site is big enough (just) to put 600m of pipe in but would need to be under drains and cables etc so to save any hassle I think borehole is the way to go and I'm being told they're more efficient 200m down instead of 600m of pipe.
Or just put air source in and have more money for the build . Either way the RHI will pay for them but the ground will make a wee bit where the air will just pay itself over 7 yrs.
So is ground source that much better it's worth paying the extra or just bang in air source??
We're building a 2 storey timber frame house this year triple glazed windows good insulation under floor heating both floors etc.
I always wanted ground source heating but it's a good chunk more expensive and I think I'd go with a borehole rather than ground collector pipe. Our site is big enough (just) to put 600m of pipe in but would need to be under drains and cables etc so to save any hassle I think borehole is the way to go and I'm being told they're more efficient 200m down instead of 600m of pipe.
Or just put air source in and have more money for the build . Either way the RHI will pay for them but the ground will make a wee bit where the air will just pay itself over 7 yrs.
So is ground source that much better it's worth paying the extra or just bang in air source??
Speedstar
Member
- Location
- Scottish Borders
Had a good talk to the man today that was up finishing off ours , Ground source is the way to go , boreholes work well , I think this country is not the right place for air source, it is to dampBringing this up again !!!!
We're building a 2 storey timber frame house this year triple glazed windows good insulation under floor heating both floors etc.
I always wanted ground source heating but it's a good chunk more expensive and I think I'd go with a borehole rather than ground collector pipe. Our site is big enough (just) to put 600m of pipe in but would need to be under drains and cables etc so to save any hassle I think borehole is the way to go and I'm being told they're more efficient 200m down instead of 600m of pipe.
Or just put air source in and have more money for the build . Either way the RHI will pay for them but the ground will make a wee bit where the air will just pay itself over 7 yrs.
So is ground source that much better it's worth paying the extra or just bang in air source??
Was that the boss or one of his workers?
The house that was built just along the road a few years back is air source and he was raving about his the other day when I asked him about it .
I think ground will be the way to go but it's 15k ish more so is a big chunk to find at the start
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