Browse Forums Heating, Cooling & Insulation 1 Apr 27, 2011 10:59 am Does anyone have any experience with a heating system which uses warm air in the roof space to heat and ventilate the house? We have a slight condensation problem on windows during winter and I am looking at installing a Warm 'N Dry http://hvsolutions.com.au, a similar system is the HRVhttp://www.hrv.com.au). The only issue I have with it is that when you really need it to be removing the damp air (cold nights), it is not able to do any good. Unless of course that the humid air has been removed during the day. Re: Ventillation / heating from roof space 2Apr 28, 2011 2:06 am I think from what you are going to pay a 3.5kw solar system and a reversible ducted air con would fit the bill nicely. You could even find a control box tweak for it so it only works when the sun shines or the PV system is producing enough watts. 3.5 KW solar is around $8 k with the cost of energy reduced it pays for itself. A 2.5KW reverse cycle ducted air con would be around $3k installed. A bigger one is around 4.5kw which is in my mind questionable, if you need this then your house is too big or inefficient. Solar hot water panels are $1500 each. 2 of them are the same as a 1.5kw solar system in price. Re: Ventillation / heating from roof space 3Apr 28, 2011 6:40 am Thats not quite what I am after - I need to remove condensation and any heating that I get will be a bonus. The cost I have been quoted is $1600 installed, so much much cheaper than PV. We already have ducted gas heating, but that hasn't fixed the problem. Re: Ventillation / heating from roof space 4Apr 28, 2011 2:14 pm Funny I was thinking about this very topic as I was dripping with sweat up in the roof today. I am in the process of cleaning out our roof space to (a) get rid of 100+years of dust (b) replace old and inadequate insulation and (c) make the space more usable for storage while we rennovate. Yesterday was quite a cool day in melbourne but it was damn hot up there...today is worse. I was wondering about the possability of installing a couple of extraction fans up there to draw down the heat during the day to heat the house. You would have have some filtering in line as it gets very dusty up there. I'll check out those links Re: Ventillation / heating from roof space 5Apr 28, 2011 2:21 pm The condensation is heat being lost to window panes and then outside. Its not the cause, just a symptom of. The heat is simply going through phase transition giving energy off and leaving moisture behind. Firstly if the moisture is excessive then you must have a source from somewhere. Bathroom, laundry, kitchen, drying clothes inside? If 5 or more people live under the roof then you can expect this. Try opening the house up during the day and allowing it to ventilate. If you can't do that then try heat exchangers and try more capable thermal barrier curtains. http://www.villavent.co.uk/heat-recover ... lators.htm http://www.passive-house.co.uk/products.htm Re: Ventillation / heating from roof space 6Apr 28, 2011 4:10 pm Redman, do you think that double glazing our old double hung timber windows would be effective? I think I read somewhere that double glazing gives the most "bang for your buck" regarding insulation even though it is also quite expensive. This would also help our condensation problem, yes? Re: Ventillation / heating from roof space 7Apr 28, 2011 10:41 pm To a point. You also have to consider weight of the double glazed units. Thicker curtains would do "as much" in regards to heat transfer but I believe on price point it might be similar for either. If sash windows are in place there are added weights and frame thicknesses that could make it a no go. Are all windows suffering condensation or is it limited to ones on a southerly aspect, perhaps in a corner shaded during day time? I found this was true in my parents house (my old room). Re: Ventillation / heating from roof space 8Apr 29, 2011 7:08 am In terms of double glazing, I would replace the existing windows completely with new ones. The cost will be worth it in the long run. The windows that get the condensation mainly are the bedrooms, which are at the southern end of the house. With the ducted gas heating, it has reduced it a little in the bedrooms, but moved some condensation into the living area. I guess helps somewhat in that the problem is "diluted". Re: Ventillation / heating from roof space 9Apr 30, 2011 2:52 pm Basil11 I think if we regularly maintain our home items like Chimney then no problem of heating of roof space. Heating of the roof space has little to do with a leaky chimney. It's a problem of metal or tiled roofs collecting heat and radiating it down. 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