Roof Space Ventilation

maxxpowa on 05/01/2020 - 11:11

We live in a double story house with ducted refrigerated cooling. As you can imagine, on hotter days the upstairs area gets quite warm and when the temperature goes north of about 35 the system starts to struggle to keep the upstairs cool.

I have been reading about ways to help, and came across solar roof ventilator fans. Basically, when the temperature in the roof hits a certain temperature the fans activate and pump out the hot air from the roof - apparently helping keep the roof space cool and thus keeping the house cooler and allowing the AC to work better.

But I have also found a few articles that mention that these are not a good idea - it can cause the house to be colder in the winter?

Im leaning towards the side of installing the fans - but I am interested in knowing if anyone has any experience or feedback on these?

Thanks!

p.s. also posted this on the whirlpool forum if you see it there.

Home & Garden

closed Comments

  • Melb69 on 05/01/2020 - 11:14
    +1

    Bulk up the roof insulation.

    • maxxpowa on 05/01/2020 - 11:41

      Our roof insulation is pretty good - but could be worth a go. I think the main reason its suggested with ducted cooling is that the fact that the ducts dont have to go through 60-70 degree heat before pumping the air into the house.

      • outlander on 05/01/2020 - 13:24

        See if you can borrow a temperature gun. You might have gaps in places where the heat is getting through.

        Roof fans aren't a bad idea, but people underestimate how big the roofspace is. You need some serious air moving through it to cool it down, which means serious power. But, as always, it depends on your personal circumstance. Tile roof, probably not worth it. Tin roof, probably worth looking into.

        • maxxpowa on 05/01/2020 - 21:10

          Why not worth it with a tile roof?

          • outlander on 05/01/2020 - 21:27
            +1

            @maxxpowa: Tile roof's are open by design. So as the outside air cools down, the roof cools down with it. While tin roofs are closed in, so any extra ventilation may help. But I'd still say borrow a temperature gun first. Most insulation isn't applied correctly, and any open patches will let heat flood through.

            Like how a boat needs to be a completely sealed to be useful, where even a tiny hole in the wall will let a disproportionate amount of water through. You can try to make it so the boat doesn't sit as high in the water, which will definitely help reduce the pressure of the water coming in, but its more effective to just find the holes and patch them.

      • Captain Musty on 06/01/2020 - 13:49

        The air intake (called the 'return') is inside your house, not in the roof-space. That way, your ac unit receives already cooled air to cool further.

        • [Deactivated] on 07/01/2020 - 13:38
          +1

          If the ducts aren't particularly well insulated though they can be affected by the heat in the roof space, as the return air and cooled air both have to transit the roof space in ducting.

  • bmerigan on 05/01/2020 - 11:18
    +5

    Haven't experienced solar powered ones, they sound good. We have a roof 'whirly-bird' vent.
    They say they're good for winter too to stop moisture build-up and the potential for mould.

    • maxxpowa on 05/01/2020 - 11:41
      +1

      Main reason I am looking at solar powered is that I read they move way more air than a standard whirlbird.

      • darshu on 05/01/2020 - 12:46

        I am also thinking about installing solar roof ventilators, some have automatic switches to turn OFF when the temperature is less than 24'c. Their warranty for the motor is only 2-3 years.

        • maxxpowa on 05/01/2020 - 12:55

          Have you been looking at a particular brand?

          • darshu on 05/01/2020 - 13:06

            @maxxpowa: I was reading about SolarArk ventilators, particularly SAV30 model. One is big enough for the whole roof.
            10 year warranty for the solar panel and 3 years for the motor. It has a thermostat to shut off when the temp is below 24'c. bit expensive though, around $700.
            https://www.solarark.com.au/wp-content/uploads/2019/09/Solar…

            Do you have solar panels on your roof?

            • darshu on 05/01/2020 - 13:06
              +1

              @darshu: And I have no idea how to clean the solar panel when its get dirty.

            • maxxpowa on 05/01/2020 - 13:39

              @darshu: No I dont have solar panels.
              The SAV20 looks like it might do what I want - good warranty too for a solar unit.
              Thanks!

        • mihali on 11/02/2020 - 17:22

          Hi darshu,
          We installed a solar System and Solarking solar fan last week, both works fantastic the fan helps to take the heat out of the roof and save even more on electricity 👍 very impressed. once refer this
          https://www.solarking.net.au/product/solar-roof-vent

  • Ocker on 05/01/2020 - 13:01
    +1

    Wed have 2 units installed - a 240v unit with a variable thermostat to enable you to select when it cuts in, and more recently a solar unit that has the thermostat set at 25 degrees
    Both units move a considerable amount of air than the el-cheapo wind driven units.
    There are some websites that provide the formula to determine the air flow volume you should install depending on the size of your roof cavity.

    • Melb69 on 05/01/2020 - 13:12

      Have you noticed any difference in the way the AC works or cooling affect inside since you had them installed.

    • deal88 on 06/01/2020 - 10:08

      We have the 240v Edmonds AiroMatic. I have noticed a big difference. Deals with heat and humidity.

      https://www.edmonds.com.au/campaigns/airomatic

  • Ocker on 05/01/2020 - 13:19

    House, single storey with a high roof and of about 300sqmt, was about 2-3 degrees cooler after the exhaust fans were installed. As they were installed before the aircon cannot make a before/after comment on the impact on the aircon.
    Something to bear in mind is that if you try and extract too much air from the roof cavity you may need to install inlet vent in the eaves.

  • YippyKiYay on 05/01/2020 - 14:10

    There's a heap of info in regards to types of insulation, roof ventilators and their effectiveness on whirlpool. Some of it gets pretty techy and in depth but IMO it's worth a read before committing. If you CBF/TL/DR, the jist of the message is that it is more effective (but more expensive) to stop heat getting into the roof space in the 1st place vs attempting to remove it via ventilation afterwards.

  • oscargamer on 05/01/2020 - 18:13
    +3

    If you install the solar vents (or any roof vents) just make sure you have some louvres or other points/vents that air can enter the roof space, to replace the air that's vented out, otherwise, you'll have a fan spinning and moving zero air.

  • brad1-8tsi on 05/01/2020 - 18:44
    +1

    I've had whirlybirds in 2 houses and they work well providing that air has a way in. (Under-eve vents or similar).

    Winter temperatures weren't an issue in the house as I had double thickness fibreglass batts so the roof space could get as cold as it liked.

    It does help if the heat doesn't enter the roof space in the first place. I had a 2nd layer of sarking with the foil side pointing outwards and this stopped a lot of radiant heat from the terracotta tiles.

  • Hoju on 06/01/2020 - 08:38

    We moved into a place with similar setup but I refuse to use the aircon as it’s both expensive and I cringe at seeing our power supply go up. We have the roof vent fan thing as well but I feel it does nothing, it must get to 40 degrees up there!

    I had velux roof windows installed and it has made more difference than any aircon could. One on each side of the roof, pop them open and the breeze flows through and the hot air out

    Also let’s light in and is an attractive feature… about $3000 for two large ones but price vary depends on size and opening style…

  • Androo305 on 07/01/2020 - 00:51

    We installed a SolarWhiz 2100 and haven't looked back. It has helped reduce temperatures inside by approximately 2 degrees and has reduce our electricity usage at the same time, ducts have less heat soak. Apparently it's equivalent to 21 whirlybirds.

    We opted for night mode and adjustable temperature thermostat. It cuts in and out at 27/28 degrees, during the day runs via solar and at night or if there isn't enough light it reverts to electricity. 6 eave vents also installed.

    It's also great for reducing mould and moisture if it's an issue. One thing to note is in winter it hardly does anything unless it gets over the set temp, which in turn helps keep warmth in where whirlybirds continuously spin.

    www.solarwhiz.com.au highly recommended.

    *We installed it 4 years ago and I hear it humming away still no issues!

    • ando213 on 07/01/2020 - 08:57

      Would you be able to let me know how much you roughly paid for the whole system and installation? Thanks.

      • Androo305 on 07/01/2020 - 15:19

        It was $1,600 from memory. Definitely no more than that.

        At the same time i did get quotes for whirlybirds (Twista) and they came to just under $1000 for 2.

  • heremaia on 25/01/2020 - 17:52
    +2

    I have installed Solarking in my garage. It’s a flat roof metal garage and used to get very hot. The fan works wonders and is certainly a big improvement. To make it even better I have added a small solar controller and 12 volt battery. This way you get a constant speed and it operates into the evening as well. Still uses the inbuilt thermostat to cut on/off at something like 25 degrees
    https://www.solarking.net.au/product/solar-roof-vent highly recommended.

    • mihali on 27/01/2020 - 18:51

      Solarking is a good unit to go with, They have reduced our lounge temperature (Cathedral Roof) by 8 -to 10 Degrees compared to the old Whirly bird – No needed the aircon this afternoon for the first time ever on a plus 30 degree day – its good

  • deelaroo on 31/01/2020 - 23:42
    +2

    In the US they seem to use insulation at the actual roof not ceiling with the idea of keeping heat out of the roof space as much as possible. Blows my mind that here we let our roof space get to 60+ degrees and wonder why inside is hot then. My next build definitely adding this for the sake of a few bags of insulation and some string is worth it.

    • Euphemistic on 14/03/2020 - 15:42

      If you insulate the roof really well it might stop the house cooling as well. So after a few days of heat the house will stay hot for longer.

      I wish our insulation could be removed every evening in summer when it cools down to drop the temp of the house quickly.

  • MilkDrinker on 14/03/2020 - 01:03

    So the airomatic has an automatic function that starts it up when it gets too humid/hot in the attic when its installed. Might be worth a look. Interested in what you have found so far

  • mihali on 05/04/2020 - 20:20

    Yes, it is effective. We have turned our aircon on once since we have had them installed. The one up the hallway above bedrooms is a lifesaver!

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