 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Solar : Cooling Opinions.
  Page 2 of 2 |
|||||
| Author | Message | ||||
| Phil23 Guru  Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
I don't have evaporative, we're too humid for it to work very well. Many end up pulling it out. I've got 2 RC's here, both 8kW; one a single head, the other a multi with 3 heads attached. What's always interest me regards evaporative is the idea of getting a discarded unit, installing it with no ducting & running it in reverse, simply as a huge extractor fan. All comes down to how much power would be used in relation to how much load would be taken off the RC systems. Phil. |
||||
| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Dunno about the overhead "Itch" factor in the heat. That and the fact that I suck the hot air down in Winter Have wondered how effective some of the foamy bubbly silver stuff on rolls I've seen at Bunnings is though. Easily installed & Particle free. About 1/2" thick & is offered in different grades. Just didn't realise how expensive it was for a roll..... Phil. |
||||
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Skymaps is a very different animal you need to be onsite but don't need to guess hights etc just set it up and point your phone to see where the sun will be. It is actually designed for looking at the stars and working what is what but the sun is a star. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024 |
Hi Phil Just thought i would try the ceiling temperature compared to the ambient temp in the house, and its about the same. There is less than half the ceiling space you have, the only reason it is cool I think is the aluminum foil I put over the foam bats, no room to move up there so had to take all the tin off the roof to get the job done what a PITA is was, shiny side up blue side down come from bunnings, before that roof insulation rebate thing started. Have 2 exhaust fans (covered in winter), I don't use them, any heat from the fridge's stove or other just finds it way around to them and out. Running 2 small air cons 530w each helps keep this place livable at 28deg and 40deg outside on hotter day's I need another aircon just to keep up. The fan in the manhole cover sucking the heat back down in the winter works great. Cheers Aaron Cheers Aaron Off The Grid |
||||
| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
For anyone else like myself, who likes scrolling thru pages of data, Here's a copy of the CSV log file that records temperatures at 7 different locations. Note the ambient, TmpChAmb, is a pooly located sensor, just below the top of the gable, mostly shaded, but above a skillion roof. Phil. Edit: Data goes back to July 2017. 2018-01-25_070019_HeatLog.zip |
||||
| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Now we are 3 pages into this, I have to ask the question, How much do roof temps matter to the house anyway? Heat rises so the heat would be and would stay above the living areas and if you have ceiling insulation, what is the effect of a hot ceiling on the living areas? Is one actually achieving anything going to all this trouble or are you going to make the house 1 oc cooler on a 40o day? In my observations, in a house that is insulated to a decent degree, the heat intrusion from windows and doors is going to leave anything coming down from the Ceiling for dead and basically render it a completely moot point. IS cooling the roof space something proven to be effective or just something that we feel is a good thing to do? This is a good idea and done properly, You could have your cake and eat it too. If you used the foam on the BACK of the bearers, you could create a space between the tin and the foam. If you sealed this off, you could Push hot air down and out your non sealed eaves to help further with the cooling. In winter you could pull the air back up ( assuming ducting near top of roof) and draw the heated air into the house. All you might want for the extraction is a 2 way Duct as used in Air con with a motor to redirect the flow. Have it so you could draw or pull one way which would be from the outside air and the other way which would be inside. This way when ventilating in summer you pull the air from outside so you are not drawing hot air in or pushing cool air out and in winter you can push the air into the home. I'm thinking reversing the fans but with this you could have it so the fan was only running one way and either pushing hot air to the outside or to the inside of the home. They call these things dampers I believe and you would want a 2 way. You could probably pick them up 2nd hand when they did a refit on a place or buy one new. They aren't exy if you get them at the right price from a wholsealer. Look on fleabay for the foam. Plenty there and much cheaper. Bunnings would have to be about the most exy place to buy that stuff. You could also try an AC supplier. They use it for covering ducting etc. Had a big roll of it myself a mate who does AC gave me. It's just foil backed foam. You should get the special foil backed tape for sealing it together as well. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Cooling the roof space makes a massive difference. A hot ceiling radiates infrared downwards which heats up everything else in the room. Kind of like grilling a steak.... Its a slow process, but over several hours it can turn a room into an absolute oven. Another thing worth looking at is "solarcool glass". This is the stuff all modern high rise offices and commercial buildings use. From the outside it looks like a silver or bronze mirror, but from inside you can see out quite clearly. It also offers complete privacy during the day, but at night you still need curtains or blinds. If you have any large windows that get direct full sun and would be difficult to shade, the solarcool glass is well worth the trouble. I have this on a west facing bedroom and it made a huge difference. Cheers, Tony. |
||||
| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
|
||||
| M Del Senior Member  Joined: 09/04/2012 Location: AustraliaPosts: 155 |
As I wrote earlier, venting the roof space by using fans etc and adding insulation has cooled my ceiling panels by over 30 degrees, heat that would have radiated down to some extent. This has allowed me to use a a 700w/2.3kw portable air con to cool the house except when she opens a window for fresh air. Yet to shade the northish side of the house with trellis/vines/shade cloth etc which will drop the pm heat load and all but negate current use of the A/C if lucky. Mark |
||||
| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
I have many times felt the ceiling on hot days. I have batts in both the old place and where I am now and never noticed the ceiling to be hot. at the old place where the walls were insulated and the place was up on piers, VERY different story. You could as you say feel the heat radiating through. Do you know of any studys/ data that shows the amount of heat radiated though an insulated Ceiling? I'm just having a difficult time with a mental picture of there being that much heat transfer when the ceiling is insulated. This one has sarking under the tin and batts on the ceiling. Ant heat that does get in is staying there atm that's for sure. Hard to vent this one. I spoke to AC mate a few months back about putting in a duct that pulls from the outside into the fan of the ducted AC. He pointed out the size of the eves and that there would not be a very big space to put an intake grill in. I have since noticed the front Verandah which is of course much wider and the roof is more or less one Piece. I'll have to get up and see if I couldn't put a grille there. Would also be a good spot to do what I suggested with the 2 way damper to extract hot air either outside ( if it is significant) or into the house like I had before. |
||||
| Alastair Senior Member Joined: 03/04/2017 Location: AustraliaPosts: 161 |
George et al Long time ago we purchased a brick veneer/tile roof house which had no insulation in the roof apart from the simple sarking. For the last months of summer we felt the heat radiating down badly. At night the place did cool quickly though. In winter the place was freezing and we quickly found the money to put in pink batts - all the rage at the time. made a big difference but on very hot days it was still hot to touch the ceiling. Opening the manhole was like the gateway to hell. I put in a couple of whirlybirds and it made another big improvement. When we cold afford to put in a/c I quizzed the guy about an intake vent from the outside and he said he would not do it for 2 main reasons. First we were in a bush fire prone zone and it could be a big risk and second it would be too easy to compromise the system by having the baffle switched wrong. My problem I said but he refused to even give me the parts to do it myself. I never did. Re another comment about using a bathroom or kitchen extraction fan to aid cooling the roof space. It is now contrary to building regs to have any vent into the ceiling space they must go external - apparently to reduce moisture into the space and reduce fire risk. I am told that whirly bird type vents are also now discouraged due to fire risk. They provide a big draft pathway if a fire gets through the ceiling. Cheers, Alastair |
||||
| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I can vouch for the difference venting the roof cavity makes, one of my previous houses had dark brown fake tin tiles on the roof (possibly the WORST idea ever- leakage potential of tiles, and the heat transfer of steel uggh) and it had NO insulation of any description, not even sarking under the fake tiles All it had was the plasterboard ceilings, and they only gave a couple of hours respite before the rooms started heating up (this place was that bad that by midday, the water out of either hot or cold taps was actually the same temperature- blister forming hot) Fitted ceiling batts and they helped a bit, but the problem remained that the roof space was still boiling hot and they merely slowed the heat transfer, not stopped it. Finally fitted 4 spinners, and under eave vents about 50cm x 20cm along the south wall, about 8 from memory, which ws obviously shaded, and also fairly well covered by a massive 'garden' ie the bloomin jungle we called it That was the single best thing we did, made a huge difference to the inside house temps and the cold water tap now actually delivered cold water, instead of being used to make coffee with That house used to get hot enough to melt the candles on the fridge (got a lot of blackouts being rural) they would still be upstanding at the base then kinda 'doop' over in a gentle s shape until they ran flat along the top of the fridge, that stopped happening after the vents went in- we were also able to drop the fridge from max back to about 3 (out of 6 or 7)- so about half- the electric bill also dropped significantly |
||||
| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
I think that time of our Forum is out a bit or date. Edited by Boppa on 26 January 2018 at 12:48am and my entry is about 19:24 25th Jan 2018 George |
||||
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I had to remove the time offset in my profile since Gizmo has moved and changed the 4M hosting. I'm confused, no wait... maybe I'm not... |
||||
| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Anyone familiar with the thermal physics concept of T to the fourth? As in Delta Temp to the power of 4? Many memories of the theory are vague these days. Phil. |
||||
| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Dammit, where did I leave the keys to the delorian??? :-) |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If lost it that is okay Jaycar sell flux capacitors. While you are at it try to straighten out Biff (aka donald trump). There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Page 2 of 2 |
|||||
 Print this page |
