Wetbacks/home heating (2 storey house)

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Jeeves

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#111520 6-Nov-2012 12:25

Hey,

We just bought a house in auckland and have been thinking up efficient ways to heat it.

It's two storeys, and the main problem is the living area is on the upper floor, and the bedrooms down below.
The ground floor is partially underground as it is on a sloping section and the front half of the ground floor (It's a rectangle shape) is underground up to a maximum height of about 1.5 meters.
Because of this, the bedrooms, especially the master bedroom which is on the south side, get very little light and heat - so can be kind of cold and damp during winter.
The ground level is all cinder block, and the upper level appears to be well insulated - so insulation seems to be in check (short of dbl glazing). The floor between the levels is also insulated from what i can tell.

So we are very keen to put a fireplace in, as the living area is well suited for one and we both love the ambience of a fire.
I was thinking of getting a wetback, and installing a radiator in at least the master bedroom to get some of that heat downstairs.
Can I do that? Given the old heat rises thing. I'm assuming a pump of sorts can override the thermal rise.
Also our HWC is on the ground floor at the opposite end of where the fire would go - talking about 10+ meters away. Is this too far away to run piping too?

The other issue I face is air movement. Again the master bedroom has little in the way of ventilation, so trying to figure out the best way to get some air movement going through there. Could I install an HRV/roof space fan thing, and then have a pipe running directly to a lower floor vent. I realise that won't do anything heating wise, but would hopefully help with moving air.

TIA :)

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#712844 6-Nov-2012 12:40

I had a fire in my house, but I took it out for a few reasons:
- They're a pain in the butt to constantly feed
- They're messy
- They're expensive to run if you don't have free wood
- When they're turned off the huge hole in the ceiling makes your house cold in winter and hot in summer

All in all I think fire is about the least efficient form of heating.

Given what you've said I'd see if you can get a heat recovery ventilation system combined with a ducted heat pump. Can you fit them in, or would it be too difficult with how it's built?

The Fujitsu sleep pump (may have that name wrong) may do the job. You want one that you can run as a ventilation system or a heating/cooling system. I have a standard ventilation system, non heat recovery, it keeps the house fresh and dry all year round, and on sunny days brings heat in too. On overcast days it doesn't provide much if any heat, but pushing the damp air out means the dry air is easier to heat.

chevrolux

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#712877 6-Nov-2012 13:32

I have to completely disagree about fires being bad. I put a fire in last year and absolutely love it. Fair call about the expense of wood. Although for $700 I get enough wood for about 1 and half winters - only had this last winter to judge it by but I have enough wood left over now for at least a half another winter I would guess. I think this is very comparable to the increased electricity costs of a heatpump over the winter period. I planned on hooking up the wetback to my cylinder. Problem I had is that it is a very old cylinder and wasn't able to be wetbacked. This was going to mean another $1000 for a new cylinder which just wasn't worth it for us as we don't plan on being in the house long enough to make the pay off worth it. As for mess, yes they are messier than a heatpump but the heat they can produce is just amazing. I am putting in a ventilation this summer as I found the lounge was getting far too hot with no ventilation system. So we will pump excess heat out to the bedrooms and bathroom.
A small thing is the 'approved' wood burners these days aren't allowed to burn overnight in an urban enviroment - that was my council's law here in Palmy. Others may be different. Wasn't a hard fix though - the air inlet was adjustable so I can now have mine burn overnight, just wasn't allowed to tell the inspector that.
At the end of the day I really think it is down to personal preference. There is just something really nice about the heat from a fire that a machine on the wall can't give you. It all depends on whether you like just pressing a button or lighting the fire.

timmmay

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#712881 6-Nov-2012 13:36

That's a good point - fires put out awful air pollution that you subject all your neighbours to.

Personally I just want the heat, I have enough other things to do that I don't need to play with fire for entertainment or ambience.

A friend has a fireplace with an inlet to his DVS above it. That distributes the heat quite well. It's also a two storey house, so putting a DVS into that kind of place should be possible.

Ventilation may be more important than heating. I'm a big fan of heat pumps, and if I build a house I'll have one big ducted heat pump for the whole house.

mattwnz

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#712886 6-Nov-2012 13:40

timmmay: That's a good point - fires put out awful air pollution that you subject all your neighbours to.

Personally I just want the heat, I have enough other things to do that I don't need to play with fire for entertainment or ambience.

A friend has a fireplace with an inlet to his DVS above it. That distributes the heat quite well. It's also a two storey house, so putting a DVS into that kind of place should be possible.

Ventilation may be more important than heating. I'm a big fan of heat pumps, and if I build a house I'll have one big ducted heat pump for the whole house.

It is far more energy efficient to have a underfloor heating supplied by a hot water heap pump. That way you are heating a thermal mass, rather than just the air. Double/triple galzing and extra insualtion is a must. Go well beyond the minimum standards for insulation.

timmmay

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#712893 6-Nov-2012 13:47

mattwnz: It is far more energy efficient to have a underfloor heating supplied by a hot water heap pump. That way you are heating a thermal mass, rather than just the air. Double/triple galzing and extra insualtion is a must. Go well beyond the minimum standards for insulation.

Oh yeah with a new build I'd get a UK builder in, NZ is so primitive for insulation and energy efficiency. We still do aluminium windows, UK has had PVC with a huge air gap for many years, sometimes triple glazing. Under floor heating is great, so long as there's insulation between the stone floor and the soil under the house so you're not trying to heat the planet, polystyrene is meant to be good. Ventilation, heat recovery, passive heating, there's so much that can be done that few places in NZ considers.

BuzzLightyear

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#712927 6-Nov-2012 14:28

Sounds like you have a very similar home setup to me. Rectangle house nestled into a hill side with part of downstairs being underground. Block construction. Only real difference being that all my living areas including bed rooms are upstairs.

I will have to disagree with a number of the other posters here. I have both modern heatpump setup and a modern efficient wood burner (2 years old). The wood burner is far, far cheaper to run over winter. I also have a wet back which makes a huge difference to hot water heating costs. The only time we use the heatpump is summer for cooling. We primarily use the fire after 3pm and on weekends. I use about $300 worth of wood every year (max). I swear by the wood burner and can honestly say it save my family a fortune in heating costs.

I think part of your problem RE the wet back installation is distance to the cylinder. I'm not an expert but I think the distance is too long to work efficiently. My cylinder is about 3 metres form the wood burner and on the same level. If I understand you correctly you want to have the fire upstairs and your cylinder downstairs. I don't believe this will work. I am pretty sure they have to be close to each other and only a slight angle allowed between the height of the cylinder and the fire place for the flow of the pipes to work.

In all honesty if you want a fire to heat upstairs living area - go for it. For downstairs you would need to either choose an efficient way of circulating the warm air or have an alternative heating method. I suspect the wetback option is a no go unless you are prepared to move the hot water cyclinder.

As a side note I do remember that wetbacks put extra strain on the cylinders so you need to make sure your Hot water cylinder is up to it.

mattwnz

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#712931 6-Nov-2012 14:31

timmmay:
mattwnz: It is far more energy efficient to have a underfloor heating supplied by a hot water heap pump. That way you are heating a thermal mass, rather than just the air. Double/triple galzing and extra insualtion is a must. Go well beyond the minimum standards for insulation.

Oh yeah with a new build I'd get a UK builder in, NZ is so primitive for insulation and energy efficiency. We still do aluminium windows, UK has had PVC with a huge air gap for many years, sometimes triple glazing. Under floor heating is great, so long as there's insulation between the stone floor and the soil under the house so you're not trying to heat the planet, polystyrene is meant to be good. Ventilation, heat recovery, passive heating, there's so much that can be done that few places in NZ considers.

I agree that NZ is primative in some areas, but that is partly because there isn't much competition in the materials market in NZ, which is one reason materials in NZ are so expensive. You can now get thermally insulated aluminum windows, which have a thermal break in them. PVC windows are ok, apart from looking ugly, but not sure on their durability, especially in NZ where we have harsh sun and UV conditions.

timmmay

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#712935 6-Nov-2012 14:40

One thing I found when I had a fire was it was good at heating one room, but the heat didn't really move to other rooms. If you're open plan, or have a ventilation system, that should be fine. They're also slow to get started.

UV Windows have been fitted up in the mountains in NZ for 20+ years and still apparently look at good as new. Aluminium with a thermal break costs more, it's not really an appropriate material.

mattwnz

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#712958 6-Nov-2012 15:02

timmmay: One thing I found when I had a fire was it was good at heating one room, but the heat didn't really move to other rooms. If you're open plan, or have a ventilation system, that should be fine. They're also slow to get started.

UV Windows have been fitted up in the mountains in NZ for 20+ years and still apparently look at good as new. Aluminium with a thermal break costs more, it's not really an appropriate material.

20 years though isn't long. I have seen anodized aluminum windows that are 40 years old and still look really good. Would agree though that powder coated aluminum isn't as good, as the coating will fail at some stage and need reapplying. I have found that PVC windows in NZ are expensive, compared to aluminum, although they are probably about the same as thermally isolated aluminum windows. I would consider anodized aluminum windows with thermal breaks as probably one of the better materials to use for windows in NZ, also due to availability and builders being more familiar with them, and can't really see any negatives with them.

timmmay

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#712960 6-Nov-2012 15:04

I got quotes, PVC costs more than standard aluminium but less than aluminium with a thermal break. I also found the aluminium joinery companies absolute a**hats to deal with, slow to visit, slow to quote and some didn't even bother to send a quote. The PVC window company I linked to had fantastic customer service.

I'm not associated with any window company.

stuzzo

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#712968 6-Nov-2012 15:13

Jeeves, normally with a wetback you have the water cylinder quite close to the fireplace and slightly higher to allow thermo-syphoning. You can use a pump but the distance you suggest sounds a bit far to me to stay very efficient. One option is a wood boiler (efficient high temperature fire that heats a water reservoir) and there are some that can go in a lounge and still give the ambiance thing. With this the water storage is used to heat radiators but this would all get well up in price and perhaps a basic central heating system, particularly if you have access to gas, would be more cost effective or heat pumps etc. I have heard good arguments that wetbacks are no longer cost effective in modern building.

It is likely that the health lobby will push wood burning out of urban areas altogether in the medium term.

Jeeves

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#712990 6-Nov-2012 15:51

Thanks everyone - kind of just reinforced my thoughts.

We will still be getting a fire place no matter what. Whilst we don't have unlimited wood, we do have access to a fair amount which will last a year or two.

The main reason I thought of the wetback idea was it was the only way I could think of getting some of the heat from the fireplace downstairs. There is no way to do it with an HRV or anything as you just can not push hot air down.

Curse you physics!

mattwnz

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#713006 6-Nov-2012 16:16

Jeeves: Thanks everyone - kind of just reinforced my thoughts.

We will still be getting a fire place no matter what. Whilst we don't have unlimited wood, we do have access to a fair amount which will last a year or two.

The main reason I thought of the wetback idea was it was the only way I could think of getting some of the heat from the fireplace downstairs. There is no way to do it with an HRV or anything as you just can not push hot air down.

Curse you physics!

A heat transfer system with a fan could work I would have thought, as you are pulling the air out of one room, and pushing it into another, even if it is downstairs. It may not be as efficent, but it could still work I would have thought. Although heat rises, once a room has hot air at ceiling level, that heat would then fill the room downwards, as long as the room is well sealed, and your room isn't filled with downlighters. Fans and ducting are pretty cheap to buy off the shelf.

timmmay

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#713044 6-Nov-2012 17:32

Jeeves: There is no way to do it with an HRV or anything as you just can not push hot air down.

Of course you can push hot air down with an HRV. You have an intake duct, a pump, and an outlet, it can come out above, below, or beside the intake. It naturally rises because it's less dense than cold air.

I had the idea that instead of taking air from the ceiling cavity and putting it back in via the ceiling I'd pipe it down inside a wall and have it come up through floor ducts. I probably won't do it, but it was a thought I had.

Niel

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#713081 6-Nov-2012 18:38

The only time a heat transfer system is effective is if you get air from a concentrated heat source, e.g. a fireplace flue or a wet back. Or if it is a through-wall ventilation. Heat transfer from a room that has e.g. a heat pump, or not fulling the air directly from the heat source, cools down too much when you try to distribute it through say 6m of ducting. Been there done that.

In our new house I'll install an air circulation system rather than a heat transfer system. It will extract stale air from the bedrooms and blow it into the open living space to mix with the aircon air. Warm air will be drawn into the bedrooms through the passage, which runs from the lounge down the middle of the house and so will keep its temperature. Air will still cool down, but the cool air will not be blown into the bedrooms.

Another advantage of pulling air from the bedroom instead of blowing into it, is there is no significant draft.

But if you have a wet back or an exposed flue, then get a heat transfer system and run it (only) while the fire is going.

For sizing, bigger is better as the fan can run slower to move the same volume of air so it is less of a draft and takes longer for the fan/filter/vent to collect dust.

You can never have enough Volvos!

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