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194 posts

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# 140854 22-Feb-2014 16:06
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Hi all. 

Before winter hits I'd like to sort out the heating in our home. We have high ceilings in our living room and bedrooms - sloped with the highest point being about 3.5m. The (large) living room has a heat pump and a fireplace but the bedrooms have no heat source (they are insulated however).

Obviously a lot of heat sits at the top of the rooms, especially in the living room when the fire is going. I'm trying to figure out how to best circulate the hot air around the house. 

I'm considering putting ceiling fans into bedrooms. Just wondering how effective they are for circulating hot air in winter with a high ceiling. Wife likes the 'Fanaway' ones with the retractable blades.

The other option is one of those ducted heat transfer kits to transfer the heat from highest point in the living room through a duct above the hallway and into the bedrooms. Not sure if they are effective? Would the air be circulated downwards?

Does anyone have any experience with either options? or maybe suggest something else?

Thanks in advance for any help.



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  # 992387 22-Feb-2014 16:45
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Heat pump




Involuntary autocorrect in operation on mobile device. Apologies in advance.


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  # 992417 22-Feb-2014 17:23
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Do you have a good sized ceiling cavity?

I doubt fans will help much in the bedrooms, there won't be that much heat up there unless they're heated already. I've been told that heat transfer kits don't work that well with heat pumps, there's a loss in transmission (unless you super insulate the pipes I guess) so you end up blowing cool air into the room.

 
 
 
 


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  # 992435 22-Feb-2014 17:32
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We built a new house a few years ago.
In winter we have a woodburner for heating in the family room, so we had a heat transfer system installed with balanced output to three bedrooms, including a thermostat to extract when the family room gets above a comfortable temperature.
On reflection, this system, while it works, in our opinion was a mistake, because the bedrooms get too warm for comfortable sleep.
If we were to repeat the exercise, we would transfer the excess heat into the bathrooms, where the circulation of warm air has many additional benefits.



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  # 992436 22-Feb-2014 17:32
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timmmay: Do you have a good sized ceiling cavity?

I doubt fans will help much in the bedrooms, there won't be that much heat up there unless they're heated already. I've been told that heat transfer kits don't work that well with heat pumps, there's a loss in transmission (unless you super insulate the pipes I guess) so you end up blowing cool air into the room.


yes, I have heard that too. We usually only use the woodburner on winter nights so would only use the transfer kit when that is burning away

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  # 992981 23-Feb-2014 19:12
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A heat transfer ducted fan in combo with a living room wood burner works for us in winter.  It takes the chill off the bedrooms.  I have not found it causes the bedrooms to be too warm to sleep.  My system is integrated into the positive pressure fresh air ventilation system (not a DeViouS)  During the day the fans introduce fresh and hopefully warmer/drier air from the roof space into the bedrooms and living areas.  At night after the wood burner is fired up I manually activate Mode I which operates a damper to switch the intake from the roof space to a lounge intake near the wood burner and the hot air up at ceiling level is pumped into the bedrooms.  Then when we go to bed I activate mode II which cycles between the roof space and the lounge every 30mins.  This gives us a measure of fresh drier/cooler air and recirculated warmed air.  If the living room area drops below 15 degrees C an auxiliary 2kW electric heater kicks in from midnight to 7am when the heat pump switches on.  Yes, you need to be a certified geek to operate all the gizmos in my house.  Pity the next owner. 

Anyway, I support heat transfer systems for moving excess heat from a wood burner, I think it will be less effective with a wall mounted heat pump as they tend to circulate the warm air and there is not a lake of hot air at ceiling level to suck away.

You can build your own heat transfer ducted system much cheaper than the Bunnings type kits, make sure you use 200mm insulated ducting and a decent fan from Pacific Fans.

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  # 993020 23-Feb-2014 21:28
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This summer, I installed a heat transfer kit to suck hot air from the far end of our hallway, and blow it out directly above the heat pump, which sucks it in and cools it.

Then the cool air is blown out of the heat pump in the lounge, towards the hallway door, but it doesnt really go through the door. So the idea is the transfer kit sucks from the other end of the hallway, pulling the cool air through the hallway door from the lounge.

You loose a degree of air temperature for every metre through the attic you run your heat transfer

So for winter, I am going to install another similar system except have it suck the cool air from a vent at the bottom of the hallway, and blow it out above the heatpump.

The reason heat transfer kits work better with a wood burner is that they blow the air out at the ceiling level and it doesnt really come down to floor level. A heat pump where the air temperature may be 5 degrees warmer than the room temperature means the warm air will just stay up near the ceiling
With a wood burner, it may be moving air that is 20 degrees above the room temperature, so when it does blow it out near the ceiling, there is more hotter air coming out, and more heat will make it down to the floor level. The fact that heat rises is compensated for with hotter air temperatures being moved. 

So I havent really decided what I am going to do for winter yet. I think I will run some PVC pipe down the inside wall of a closet to a vent at the floor of the hallway and suck the cool air from there, and push it out above the heat pump to be heated. It will do the same thing - bring warmer air from the lounge down the hall and only return the cooler air back to the heat pump, rather than sucking hot air and heating it up more, only to stay at ceiling level. 

Will need to super insulate the pipework more though.




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  # 993025 23-Feb-2014 21:31
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If you wrap pink batts around the ducting do you still lose 1 degree per meter?

 
 
 
 


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  # 993038 23-Feb-2014 22:20
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I think that loss of 1 degree is just with the reflective springy pipe they come with. If you wrap pink batts around it and then use something like strong electrical tape or something to keep it tight, then it will be better.

I was thinking of replacing the springy pipe with a nice fat pvc pipe so it has less friction and less noise. Was then thinking about wrapping it in bubble foam but i just checked our hot water cylinder pipework and the foam itself is letting off alot of heat so i think pink batts is a much better idea :-)




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  # 993048 23-Feb-2014 22:31
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raytaylor: This summer, I installed a heat transfer kit to suck hot air from the far end of our hallway, and blow it out directly above the heat pump, which sucks it in and cools it. 

I did this about a year or so ago, but suck stale air from the bedrooms.  Still got to add the spare bedroom and rumpus room, in which you can feel the difference.

Acoustic/thermal ducting of ~200mm diameter is ~R0.8.  You can add pink batts, but the problem is the difficuilty in enclosing it.  You need a perfect enclosure (just like a tight fit between rafters).




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  # 993055 23-Feb-2014 22:40
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Right now, I have a the heat transfer fan in the halfway end, and a 12v computer case fan at the other end so i am trying to offset the heat absorption with air speed. but i think that springy pipe slows it down alot. 

I think if i replace the pipe with smooth PVC, and wrap it in pink batts, with large cable ties around the batts then it should work?
I have seen that the foam around our hot water piping is held on with fancy electrical looking tape, but a super long cable ties should be more permanent.

I have never purchased pink batts before but i would be looking at getting the oblong sheets?
We had the sheeps wool stuff blown in our attic a couple of years ago which is supposedly better than pink bats but i cant coat a pipe with it. But i see in new houses they have cut pink (yellow?) batts to fit into the rafters so I would use that




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  # 993103 24-Feb-2014 07:18
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Niel: I did this about a year or so ago, but suck stale air from the bedrooms.


This might be a better way to go. If I did this it would suck the warm air in through my well insulated hallway, not through the cold ceiling cavity. You can always put in a heat exchanger with an air inlet from outside to give you fresh air that's pre-warmed/pre-cooled.

raytaylor:  I have never purchased pink batts before but i would be looking at getting the oblong sheets?
We had the sheeps wool stuff blown in our attic a couple of years ago which is supposedly better than pink bats but i cant coat a pipe with it. But i see in new houses they have cut pink (yellow?) batts to fit into the rafters so I would use that


Yes, the sheets. I had sheeps wool blown in, it was a lot better than nothing, but it compacted down over a few years. I put pink batts over the top of it and it made a BIG difference.

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  # 993131 24-Feb-2014 09:16
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With regards to the OP, yes, a heat transfer kit will work wonders if you have a wood burner heat source. These heat sources usually kick out way too much heat for the one room they are in. Wood burners are often sold based on the size of the house, but with no thought given to how that heat gets from the one sweltering room to the cold rooms elsewhere in the house. A heat transfer kit solves this situation.

There are some provisos, some as outlined above:
1) You will lose heat into your roof space as the ducting is usually not particularly well insulated. Insulating this will save you money long term. Also design to have the shortest runs possible.
2) These only work effectively when you have a lot of excess heat, so they don't work particularly well with the likes of fan heaters, heat pumps, or even well sized (for the room) gas heaters. With the losses you'll do little more than circulate air and waste 'heat' into the outside world.
3) You'll want to inject the air on the far side of the room ideally, so it will actually pass through the room before exiting.
4) You'll need to keep all the doors open/ajar to allow a return path for the air. This whole system works by creating a flow of air and if a room is sealed then now air can get into it, and the air will travel another path back. This is relevant for single outlet systems right up to multi outlets. The air will find the easiest path back, and it will need a path back.

The above are just some guidelines/concepts which may help you to design the system to be most efficient.

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  # 993447 24-Feb-2014 16:52
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Loose fill insulation gets in everywhere, but is troublesome with things like LED fittings with a heat sink because typically the fill is not allowed to block the heat sink fins (batts will form a small air cavity).

If you want batts, go for Bradford Gold which is made from polyester instead of fibreglass, much much easier to work with and no breathing mask needed while you are in a hot ceiling cavity. Fibreglass is better over time, but in my opinion still not worth it for DIY.

You can do wonders with a computer fan. A couple of years ago I've posted photos of our cheap oil fin heaters with a computer fan on top, blowing the warm air down to the floor and then it spreads along the floor. Consumer products either blow horizontal so you have to sit in front of it, or it has no fan and the heat just rises up to the ceiling. Made a huge difference and our power bill dropped. The thermostat on the cheap heater also became useful, sensing room temperature rather than getting heated by the element.

Spiral ducting is to reduce noise (but even better, go for acoustic which has tiny holes in the extra, inner payer foil), a long smooth pipe will have resonance unless you make it a very large diameter like they do in central heating systems. Some air "sticks" to the spiral anyway and most of the air moves down the centre.

If you have a fire place with a flu through the room to the ceiling, instead of just mounting a vent near it you can put a shield around it and draw air over the flu using the shield. Just remember to run the fan whenever the fire is going, maybe a temperature switch mounted on the flu.

The one mistake I made was to finish mounting everything and then turning on the fan. The bedroom vents are dead quiet but the ducting from the fan to the living space is too short, causing turbulence and noise. Will have to go up there sometime to fit a longer pipe with a loop.




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  # 993450 24-Feb-2014 17:02
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Niel: Loose fill insulation gets in everywhere, but is troublesome with things like LED fittings with a heat sink because typically the fill is not allowed to block the heat sink fins (batts will form a small air cavity). 
If you want batts, go for Bradford Gold which is made from polyester instead of fibreglass, much much easier to work with and no breathing mask needed while you are in a hot ceiling cavity. Fibreglass is better over time, but in my opinion still not worth it for DIY.

 Where did you get your information that Bradford Gold is Polyester? As far as I am aware it is still glass wool.Apparently though they are now bio-soluble fibre, so apparently a lot safer.
Also if it is polyester, I doubt it can be put over the top of downlighters with IC rating, like you can with glass wool.
I beleive glass wool has better insualtion properties than polyester, or wool/polyester mixes. I would suggest a wool polyester mix, but that also can't be used over IC lights.

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  # 993470 24-Feb-2014 17:28
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mattwnz:
 
Niel: Loose fill insulation gets in everywhere, but is troublesome with things like LED fittings with a heat sink because typically the fill is not allowed to block the heat sink fins (batts will form a small air cavity). 
If you want batts, go for Bradford Gold which is made from polyester instead of fibreglass, much much easier to work with and no breathing mask needed while you are in a hot ceiling cavity. Fibreglass is better over time, but in my opinion still not worth it for DIY.

 Where did you get your information that Bradford Gold is Polyester? As far as I am aware it is still glass wool.Apparently though they are now bio-soluble fibre, so apparently a lot safer.
Also if it is polyester, I doubt it can be put over the top of downlighters with IC rating, like you can with glass wool.
I beleive glass wool has better insualtion properties than polyester, or wool/polyester mixes. I would suggest a wool polyester mix, but that also can't be used over IC lights.


Sorry, my mistake, it is Autex Greenstuf that is made from polyester.

From the installation datasheet of our IC-F rated LED down lights:
Approved: Pink Batts, Bradford Gold, InsulPro Poluyester insulation, Ecofleece, Autex Greenstuf, Earthwool, and Premier insulation.  NOT approved: Macerated paper (insul-fluf) and other loose fill as defined in NZS4246 standard is not permitted to abut or cover or be used in proximity to this luminaire and driver."




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