House building and your thoughts

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#1108040 14-Aug-2014 01:06

Aredwood: Don't use underfloor heating as your main heat source unless you have poor solar gain. Otherwise you will have annoying big temperature variances in your house. And it will waste energy. And if you want to use gas for underfloor heating get a proper condensing boiler instead of an infinity. Much more efficient.

I think underfloor is good in parts such as under kitchen and bathroom floors where you want to walk around in bare feet. In the UK underfloor heating is making a big comeback, although it tend to be the electric coil type, which is more expensive to run. They are getting away from radiators which use up heaps of wall space.

Handle9

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#1108068 14-Aug-2014 07:26

Aredwood: Don't use underfloor heating as your main heat source unless you have poor solar gain. Otherwise you will have annoying big temperature variances in your house. And it will waste energy. And if you want to use gas for underfloor heating get a proper condensing boiler instead of an infinity. Much more efficient.

This isn't correct if the system is correctly designed. If the house is correctly zoned and controlled it works well. If you do in slab you should have in slab and space temperature sensors controlling a zone manifold system.

If you run one zone for the whole house it's a different story of course. Agree about a condensing boiler, they are greatly superior to a calorifier.

Fred99

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#1108131 14-Aug-2014 09:28

A family member installed sub-floor heating on a new build 10 years ago, with diesel boiler system for heating and hot water. They have had big problems, the boiler had repeated "issues" and needed to be replaced out of warranty (I think they got some compensation from the manufacturer - the failure was related to installation somehow - and the installer was no longer in business). Now the in-floor pipes are leaking, the system can't be used. I believe the leaking is due to minor settlement/cracking of the slab, and there are disputes over who is responsible. I'm not saying that these systems aren't good - but if there are subsequent problems because something wasn't done right, then fixing those problems seems to be a very expensive exercise.

floydie

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#1108269 14-Aug-2014 11:54

i would also suggest buying a roll of 12mm strapping tape (that blue stuff) and run loads of draw wires in your rooms where you may want power/network in the future its dirt cheap and will save loads of hassle running wires later down the track. simply staple gun them to the top and bottom plates.

DarthKermit

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#1108280 14-Aug-2014 12:16

Fred99: A family member installed sub-floor heating on a new build 10 years ago, with diesel boiler system for heating and hot water. They have had big problems, the boiler had repeated "issues" and needed to be replaced out of warranty (I think they got some compensation from the manufacturer - the failure was related to installation somehow - and the installer was no longer in business). Now the in-floor pipes are leaking, the system can't be used. I believe the leaking is due to minor settlement/cracking of the slab, and there are disputes over who is responsible. I'm not saying that these systems aren't good - but if there are subsequent problems because something wasn't done right, then fixing those problems seems to be a very expensive exercise.

I guess that could happen with any piping systems embedded in the slab: water, drain, sewer.

Whatifthespacekeyhadneverbeeninvented?

timmmay

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#1108282 14-Aug-2014 12:18

Overspec your insulation, internal noise insulation is a great idea too. Double glaze every window, PVC windows seem to be best. I'd go for a central heating/ventilation system with a heat exchanger and some way to centrally shut off which rooms are being included - no point heating rooms you're not using. Have a big double heat pump type thingy outside, somewhere hidden. I wonder if it's practical to pipe in from under the house, through ducts in the floor, to avoid the heat loss through having big holes in every room's ceiling.

If you want a greenhouse think about where you'd locate it before you build (niche I know, I just built one somewhere not ideal). I love having a separate office. Also love our custom designed wardrobes, done by Boston who have branches in major centres. I'm liking the idea of two storey, upstairs for sleeping and such, downstairs for living and entertaining. Think about where all furniture, appliances, speakers, TV, etc will go.

There's a decent enough free 3D design package called sweet home 3d which was great when I was designing a new bathroom, really really helped. Probably not as good as commercial but worked great. Takes a bunch of time but really helped me visualise things.

Fred99

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#1108353 14-Aug-2014 13:06

DarthKermit:
Fred99: A family member installed sub-floor heating on a new build 10 years ago, with diesel boiler system for heating and hot water. They have had big problems, the boiler had repeated "issues" and needed to be replaced out of warranty (I think they got some compensation from the manufacturer - the failure was related to installation somehow - and the installer was no longer in business). Now the in-floor pipes are leaking, the system can't be used. I believe the leaking is due to minor settlement/cracking of the slab, and there are disputes over who is responsible. I'm not saying that these systems aren't good - but if there are subsequent problems because something wasn't done right, then fixing those problems seems to be a very expensive exercise.

I guess that could happen with any piping systems embedded in the slab: water, drain, sewer.

Yes. I'm not sure what the exact problem was in that case. From what I do know, I gather that a bad job was done. I guess that plumbing fittings/materials/methods are all well covered by legislation - not sure about in floor heating pipes. They're also covering basically the entire slab, plumbing only in some areas.
I'm kind of biased re earthquake performance. If I was to ever build a slab on grade home, I'd be wanting to ensure design and construction of the slab was really top notch, that may also impact on layout/design.

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mattwnz

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#1108383 14-Aug-2014 13:34

With network cable, make sure it is installed in conduits. This allows you to either pull more wires through in the future(if it is wide enought), or upgrade the cabling.

mattwnz

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#1108386 14-Aug-2014 13:37

DarthKermit:
Fred99: A family member installed sub-floor heating on a new build 10 years ago, with diesel boiler system for heating and hot water. They have had big problems, the boiler had repeated "issues" and needed to be replaced out of warranty (I think they got some compensation from the manufacturer - the failure was related to installation somehow - and the installer was no longer in business). Now the in-floor pipes are leaking, the system can't be used. I believe the leaking is due to minor settlement/cracking of the slab, and there are disputes over who is responsible. I'm not saying that these systems aren't good - but if there are subsequent problems because something wasn't done right, then fixing those problems seems to be a very expensive exercise.

I guess that could happen with any piping systems embedded in the slab: water, drain, sewer.

I have never heard of it occurring with any before, and the underfloor pipes are flexiable and low pressure. It sounds like it is a structural slab problem rather than one with the underfloor system. It is like saying that all weatherboarding is bad because some weatherboarding was used on leaky buildings. It is all about how it is detailed and built.

Fred99

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#1108615 14-Aug-2014 19:07

mattwnz:
DarthKermit:
Fred99: A family member installed sub-floor heating on a new build 10 years ago, with diesel boiler system for heating and hot water. They have had big problems, the boiler had repeated "issues" and needed to be replaced out of warranty (I think they got some compensation from the manufacturer - the failure was related to installation somehow - and the installer was no longer in business). Now the in-floor pipes are leaking, the system can't be used. I believe the leaking is due to minor settlement/cracking of the slab, and there are disputes over who is responsible. I'm not saying that these systems aren't good - but if there are subsequent problems because something wasn't done right, then fixing those problems seems to be a very expensive exercise.

I guess that could happen with any piping systems embedded in the slab: water, drain, sewer.

I have never heard of it occurring with any before, and the underfloor pipes are flexiable and low pressure. It sounds like it is a structural slab problem rather than one with the underfloor system. It is like saying that all weatherboarding is bad because some weatherboarding was used on leaky buildings. It is all about how it is detailed and built.

Repair of leaking in-floor "hydronic" heating seems to be big business in the US.

Aredwood

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#1109340 15-Aug-2014 22:10

Handle9:
Aredwood: Don't use underfloor heating as your main heat source unless you have poor solar gain. Otherwise you will have annoying big temperature variances in your house. And it will waste energy. And if you want to use gas for underfloor heating get a proper condensing boiler instead of an infinity. Much more efficient.

This isn't correct if the system is correctly designed. If the house is correctly zoned and controlled it works well. If you do in slab you should have in slab and space temperature sensors controlling a zone manifold system.

If you run one zone for the whole house it's a different story of course. Agree about a condensing boiler, they are greatly superior to a calorifier.

Agree on having slab temp sensors as well as room temp sensors.

But the main problem is because of the thermal mass of the floor, An underfloor heating system can't respond quickly to rapid changes in the heating demand of a room. Imagine a house that gets good morning sun. On a clear cold night the heating will be running at high output to keep the house warm. The sun then comes up and starts heating the house as well. Because the slab is still warm it is still radiating heat. (even though the room thermostat has switched the heating off) This heat is adding to the sun's heat which makes the house too hot. Over the day the slab cools down as the sun's heat and the remaining heat radiating from the slab keeps the room warm enough to stop the room thermostat switching on again. The sun goes down, Room temp drops, Room thermostat switches on again but because slab is now cold the room also gets cold due to the time taken to reheat slab.

Agree that there are ways of managing this problem. But cant see how you can have a house that has good solar gain, Which is heated solely by underfloor heating. And which is still able to maintain very close control of indoor air temp.

What I think is the ideal system - Underfloor heating that maintains the slab at say 18deg during the day and say 22deg at night. And all rooms also having another heat source that directly heats the air which is used to top up the heat radiating from the slab. And the system also incorporating a sensor that measures the strength of the sun. So that when the sun goes down or clouds / rain appear, The system can respond immediately instead of waiting for the room temp to start dropping.

Batman

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#1109347 15-Aug-2014 22:35

can someone sticky this thread?

maoriboy

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#1112359 20-Aug-2014 20:02

Here's something I forgot to ask in my initial post. Single or multi storey? What are your thoughts on basements? Is it really cheaper to build up/down than out?

Handle9

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#1112379 20-Aug-2014 20:33

Aredwood:
Agree on having slab temp sensors as well as room temp sensors.

But the main problem is because of the thermal mass of the floor, An underfloor heating system can't respond quickly to rapid changes in the heating demand of a room. Imagine a house that gets good morning sun. On a clear cold night the heating will be running at high output to keep the house warm. The sun then comes up and starts heating the house as well. Because the slab is still warm it is still radiating heat. (even though the room thermostat has switched the heating off) This heat is adding to the sun's heat which makes the house too hot. Over the day the slab cools down as the sun's heat and the remaining heat radiating from the slab keeps the room warm enough to stop the room thermostat switching on again. The sun goes down, Room temp drops, Room thermostat switches on again but because slab is now cold the room also gets cold due to the time taken to reheat slab.

Agree that there are ways of managing this problem. But cant see how you can have a house that has good solar gain, Which is heated solely by underfloor heating. And which is still able to maintain very close control of indoor air temp.

What I think is the ideal system - Underfloor heating that maintains the slab at say 18deg during the day and say 22deg at night. And all rooms also having another heat source that directly heats the air which is used to top up the heat radiating from the slab. And the system also incorporating a sensor that measures the strength of the sun. So that when the sun goes down or clouds / rain appear, The system can respond immediately instead of waiting for the room temp to start dropping.

Understand where you are coming from however in the real world it doesn't work like that. Close control of indoor air temperature is inefficient and unnecessary. You typically don't close temperature control anything except operating theatres and some laboratories. Far more common, and efficient, is to allow the temperature to swing a couple of degrees.

Solar doesn't come on and come off instantly, it does so slowly. It also doesn't have a hell of a lot of effect in the middle of winter when you actually need heating. In reality you can get nice comfort control out of underfloor heating, and has the added benefit of no draughts.

Instantaneous reactions of heating and cooling systems are avoided at all costs, especially in forced air systems as they create hot and cold drafts and discomfort. Solar (lux) sensors get used for lighting control but not for temperature control as not all the space will have solar gain, and it will change through the day. A representative space temperature sensor is the only way to effectively temperature control a space. You can use that to reset the slab temperature setpoint and it works very well.

HVAC control is what I do (well actually I project manage it, I have engineers who make it work :) ) so I have some knowledge of how it works. We're currently doing a job with about 60 zones of hydronic underfloor heating (it is a hospital not a house but it's the same concepts).

Niel

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#1112403 20-Aug-2014 20:59

Double story is nice for getting a view and for small, tight sites. However, our mortgage broker says buyers are avoiding them as it is a hassle when you get older and it is a pain to maintain (to pain or to clean the roof/gutters) and I reckon it would also be more expensive/similar to build due to health & safety equipment required or the need for a stronger foundation or deeper piles (but check this with a builder).

Solar gain in Winter is similar to Summer, the little bit of extra scatter from Winter sunlight coming at an angle through more pollution is nothing compared to the distance it already travelled through space dust. We design rugged agricultural products with LCDs which are used in full sunlight in IP67 sealed enclosures. The only real difference is that you have less hours of sunlight per day, so average temperature is lower. But solar gain is still the same (when the sun is out). You actually get more solar gain in Winter due to the lower angle letting in a larger area of sunlight through the window, when the sun is out.

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