Ceiling Insulation

I'm undecided about whether to go ahead with it or not, mostly because of fear of holding in the heat in summer.

House is not uncomfortably hot in summer, rarely need to use the aircon.

Would definitely like it warmer in winter.

Can anyone estimate how many degrees warmer the nights would be in Qld with insulation?

With thanks.

Depends upon the construction of your house. The roof space should be (almost definitely will be) ventilated. This will take the warm air out, from wind and through a chimney effect... Insulation will stop heat coming in too.

If you have got a pitched roof and put in just above the ceiling its not a problem. Also if your house has lots of thermal mass - ie. made of block, brick or stone, this will help with overheating - it gets warm the heat goes to the walls and remits at night when temperatures drop.

I'm say insulation is a good investment.

Might as well try it if it’s not going to cost much. You can always take them out again. Call an insulation mob to find out temperature ranges(might have to ring around)

Julia,
If you are worried about holding in heat during summer, then go with glass wool bats and also install a couple of whirlybird roof ventilators per roof cavity.
I found that the whirlybirds greatly decreased the roof temperature in summer and also help to remove moisture from bathroom exhaust fans.

Just make sure you install them close to the highest point on the roof on the sunny/hottest side (hot air rises) and to help catch the breeze.

Now I notice the heat conduction via the brick veneer walls more than through the ceiling.

Insulation is one thing but i found the best thing to keep the heat out (for summer) is to get your windows tinted.

Trust me, i know. I've never in my life had air-con in my house. I was painful before i got my windows tinted but now it's actually quite cool. Get the mirror tint - it blocks 70% heat and 99%UV rays

Thanks for additional responses - much appreciated.

Re tinting windows: can appreciate it would reduce heat in summer if windows are exposed, but actually almost no sun comes in via windows in summer because of deep eaves plus sunblinds externally. But it does come in during winter when sun is lower in the sky and I'd hate that not to happen.

Julia said:

Re tinting windows: can appreciate it would reduce heat in summer if windows are exposed, but actually almost no sun comes in via windows in summer because of deep eaves plus sunblinds externally. But it does come in during winter when sun is lower in the sky and I'd hate that not to happen.

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It sounds like you've already got decent passive solar design with the windows.

If that's the case then adding insulation will basically result in a stabilisation of temperatures. That is, assuming the windows are shut, no heating and no air-conditioning then the variation in inside temperature will be less than it is at present.

Answering the "how much difference will it make?" question is a difficult one in a situation where there's little heating or cooling used. It will depend a lot on house-specific factors, but realistically I'd expect that with insulation it will be cooler during the late afternoon and evening and warmer in the morning compared to not having insulation. Less heat gained during the day and less lost at night. Obviously if you're running any heating, cooling or significant ventilation then that will affect things a lot.

We have always had insulation in our roof, so I dont know what it would be like without it. Maybe it is promoted more in SA than in Queensland?

A few figures from my house today. I'm in Tas so you can't directly compare actual temps with Qld but it should nonetheless give an indication of how insulation holds the heat in.

Heating was turned off at 5:50am and I left for work at 6:20. It was 20 degrees inside at 5:50am, 8.5 degrees outside. At 6:20 it had dropped to 18.5 degrees inside, helped along by having had the extractor fan in the bathroom on.

Came home at 2:30pm and it was 19 degrees inside. Outdoor temperature now 14.4 (maximum today 14.8 on my thermometer) and it was intermittently sunny until about 1pm then overcast. I have windows facing East, North and West.

Now, quite obviously what I've done here is basically turn the house into a greenhouse. The house warmed up by itself and remained a few degrees warmer than the outside air.

I've had the heater on (3.5kW going flat out) since 2:30 and also had the oven going for half an hour, plus a few minutes use of one burner on the cooktop. It's now 21.5 degrees inside.

So overall the temperature inside is relatively stable. Even in mid winter it's generally around 13 when I get home at 6pm on a day that might have only briefly been above 10 outside. Coldest I've ever seen it inside is 10 degrees and that was after 12 hours with no heating on a completely overcast day with a maximum outside somewhere around 7.

In summer, I have only a portable evaporative cooler that's of limited benefit. But it only gets up to 30 inside when it's been high 30's outside despite the E, N and W facing windows (I close the blinds when it's hot). But on those days it's still around 25 when I go to bed and 22 in the morning with no heating.

So, in short, insulation and thermal mass will help stabilise temperatures. I've got glass wool batts in the roof, foil in the walls, nothing under the floor but it's carpeted and enclosed under. House is a fairly typical 1990's brick veneer with tin roof.

Smurf, thank you very much for such detailed observations. Much appreciated.
Is there any reason why the insulation could not be installed everywhere except over the main bedroom? Never want that warm. Even in winter, the door and window is open and the fan on (cold air, warm bed).

You might be surprised to know that morning temp inside here in winter can be as low as 12, when outside falls to around 3, 4 or 5. Previous evening heating would have brought it up to about 24.

Smurf, on an unrelated issue: what would be the likely reason for items in frig to be getting frozen when refrigerator temp control is turned to the warmer side of adjustable range? I have a vague memory of being told not to do this, that both frig and freezer should always be kept at medium temp control.

No reason why you couldn't insulate just part of the ceiling as long as whoever is installing it can work out (in the roof) where the walls are. Usally that's not too hard but in some situations it can be more difficult (though not impossible) to work it out. But if you've got the window open then it's not really going to matter a lot since the airflow through the window is a far more significant heat transfer than loss / gain through the ceiling (depending on how far the window is open, but there's a reason why it's worth sealing even small cracks in cooler climates to stop heat loss).

As for the fridge, assuming it's a two door conventional (upright) frost free fridge / freezer:

The thermostat usually controls one motor and refrigeration system for both and is usually measuring the temperature in the fridge. There are some models where all this is reversed.

When the motor runs, cold air is blown into the freezer with a small amount directed via a duct into the fridge. A baffle in the duct, adjustable via the balance control (the other temperature knob) adjusts how much cold air goes into the fridge but it's always a relatively small amount compared to the freezer.

The thermostat is the one which, when adjusted to "off", causes the motor to stop, usually with a "click" sound like an oven thermostat. The balance control, which adjusts the baffle, is the other one. The labelling on these is often highly confusing so ignore what it says and work out for yourself which is which.

Some more expensive models have completely separate refrigeration systems for the fridge and freezer. In that case, ignore all I've said here and just adjust each thermostat to get the temperature right. Most common fridges in Australia are as I've described however.

Ideally you want about -18 in the freezer and about 4 degrees in the fridge if it's for normal use.

Set the baffle to half way and adjust the thermostat to get the right temperature in the fridge.

If the freezer is not at the desired temperature, adjust the baffle to correct this. Turning the baffle down, so less cold air flows into the fridge, will cause the motor to run longer to maintain the same temperature (set by the thermostat) in the fridge. The effect of this is that the freezer becomes colder. Reverse if you open the baffle more.

It should be possible to get it about right following this proceedure. Adjust it once per day (no more) when the doors have not been opened for a few hours until it's right. In most cases though, setting the baffle half way and adjusting the thermostat to get the right temperature in the fridge will leave the freezer at about the right temp.

Be aware that running the freezer too cold may not be noticeable unless you've got ice cream or something similar that will become too hard if it's too cold. But at the extreme, if you turned the baffle right down so the freezer was extremely cold, you'll end up with some rather big electricity bills and will also be wearing out the motor etc unnecessarily. So it's worth a bit of messing about to get it right.

If putting a thermometer inside the fridge or freezer, put it amongst something bulky (eg a bag of frozen peas or in a glass of water) so that it reads the average temperature. The temperature of both the fridge and freezer will vary as the motor switches on and off - you want the average and not one extreme or the other that may have been reached just before you check the thermometer.

If there's a meatkeeper, "chill zone" or any other routinely adjustable vent into the fridge then adjusting this will upset the balance just like adjusting the baffle. I'd recommend leaving them in the same position all the time (open unless you specifically want them closed for some reason) and just adjusting the baffle to get the temperatures right. Doing this won't add to your electricity bill with most fridges.

If the fridge has a butter condioner box in the door then be aware that this is literally a heating element running 24/7. Extra power to run the element and then more power to extract the heat it produces. Leave it off unless you really do want it on.

Also be aware that there will be some means that the fridge tranfers heat to the surrounding external air. This could be a condenser coil (black metal piping) at the back or underneath. Or it could be embedded in the walls of the fridge with heat transfer through the metal casing (common in newer fridges). Wherever it is, it needs air to circulate and if it's an external coil should be kept clean - failure to do so hinders the operation of the refrigeration system leading to more running, more wear and higher power consumption.

And the obvious one, the fridge should ideally not be in the sun or near any heat source. If there's no alternative, then a white fridge will suffer less from this than stainless steel or other dark colours which absorb more heat.

Heat rises.

Not too fussed about the ceiling, what about the floor?

http://en.wikipedia.org/wiki/Underfloor_heating

thankyou for your posts smurf

nunthewiser said:

thankyou for your posts smurf

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Yes I agree. Thankyou smurf for sharing your knowledge.