Ceiling Insulation

[Julia]

I'd appreciate any comments from people who have insulation installed, e.g.

1. what kind and why did you choose that type?

2. how effective have you found it?

3. is the effectiveness more noticeable in terms of reducing heat in summer or
holding heat inside in winter?

Any particular things to look out for?

With thanks.

 

[glads262]

I'd appreciate any comments from people who have insulation installed, e.g.

1. what kind and why did you choose that type?

2. how effective have you found it?

3. is the effectiveness more noticeable in terms of reducing heat in summer or
holding heat inside in winter?

Any particular things to look out for?

With thanks.

Hi Julia,
I am in a rented house, newly built - so don't know exactly what type of insulation is in place, but I know that all walls and roof are insulated.

In winter (average 18 degree day) - we only use our heater on days when there is rain - if we can get some sunlight in the windows during the day, this heats the house to 21 degrees. By 6 oclock, cooking tea is enough to boost the temp and keep it around 21 degrees. By morning the house is usually back to 19 degrees.

So the effect is huge in winter - but if you don't get heat during the day from the sun, or cooking, you will need to use your heater to get the temp up initially.

In Summer - you basically start your aircon up later. On a 40 degree day, usually you would have to turn your aircon on the second you get up. With insulation, you can usually last until about 3pm before it gets above 25 degrees inside. So you still use the aircon full on, but for less time overall.

Hope this helps!

 

[moXJO]

tile or tin on your roof?
Is roof newish?

 

[Julia]

glads, thank you. Yes, really helpful, thank you.

moXJO, tile, 16 years old.

 

[jackson8]

I'd appreciate any comments from people who have insulation installed, e.g.

1. what kind and why did you choose that type?

2. how effective have you found it?

3. is the effectiveness more noticeable in terms of reducing heat in summer or
holding heat inside in winter?

Any particular things to look out for?

With thanks.

hi julia

being a ceiling fixer all of 33 years i would go with nothing less than a fibreglass batt
most would recommend a R 3.5 rating for ceilings
will help both ways to keep heat or cold out and keep your cooling or heating system in
it is cost efficient and fire resistant

forget blow in as imo it is absolute c**p messy and can smoulder in the event of fire
natural fibres are too expensive ; such as wool batts and i wouldnt recommend polyester either

will depend on how easy it is to access your ceiling space

hope this helps
gary

 

[Julia]

Gary, thank you. Why are you opposed to the polyester?

 

[awg]

My observation is to do with insulation effects in summer.

I recently had my walls clad, in a highly insulative material.

It was the right stuff for the job, but the insulation was only secondary.

I have found that it is actually a "heat trap" in the summer evenings, as I suspected it would be, which means more aircon on hot nights.

I do expect to save big in winter though

When I first questioned the salesperson about the summer heat trap, he denied it at first, but started mumbling when I asked further.

Passive Solar design is an interest of mine, and makes a huge difference.
Unfortunately, my home has very poor passive solar design, as do most homes.

ps Julia..I reckon you should read every single page of that BEPPA thread...

 

[Julia]

awg, I'm only considering doing the ceiling, and then only because I'm don't have to pay for it. The house is pretty comfortable in summer but does need heating in winter.

The point you raise is one I've been thinking about, and I find it hard to see how if heat is going to be pleasantly trapped in during winter, why isn't it similarly going to be trapped in summer?

 

[moXJO]

awg, I'm only considering doing the ceiling, and then only because I'm don't have to pay for it. The house is pretty comfortable in summer but does need heating in winter.

The point you raise is one I've been thinking about, and I find it hard to see how if heat is going to be pleasantly trapped in during winter, why isn't it similarly going to be trapped in summer?

With a tile roof in summer the roof space heats up a fair bit. Thus having a barrier between ceiling and roof space will prevent a lot of the heat transfer. It makes it worse if you tiles are not sarked underneath (foil backed paper).
During winter I suppose it works the opposite with the heat being trapped inside a little bit more. Having a lot of windows and areas that heat can escape or enter is something else you should take into consideration (north facing windows, large gaps round doors etc).

Depends on the area you live too

 

[awg]

the heat trap issue is affected by several variables.

including, the mode of heat entry into the house, its materials, orientation and roof/ceiling/wall characteristics.

concentrating on the roof, prevention of heat ingress in the day is good, but IMO, on hot summer nights, simple physics demand that heat will be trapped, therefore, your house will cool down much slower on very hot nights.

It has proven to be the case here.

I have fully deducted aircon, and spoilt teenagers who demand aircon at night if it is too hot

If anyone can convince you (or me), that you wont be hotter on a hot summer night, well I would like to hear how that can be.

Surprise, Surprise, they never mention this issue on the TV ads

Winter should save money.

Some people cant stand hot nights, if you have no aircon, to be borne in mind

pps BEPPA profits today alone payed my cladding bill several times over

 

[AlterEgo]

I find it hard to see how if heat is going to be pleasantly trapped in during winter, why isn't it similarly going to be trapped in summer?

To some extent it does. What the insulation basically does is to slow the heating and cooling of the house, and reduce the temp extremes. I've noticed this after I insulated my roof. ie. The house takes longer to heat up, so the air-con only needs to be turned on later in the day during summer, BUT once heated it takes longer to cool down as well. So in summer the house is cooler in the day, but warmer at night than it used to be. In winter the extra warmth at night is good, but not so good in summer.

I decided on polyester insulation, as I was concerned about the health effects of breathing in fibreglass fibres. It's a little more expensive though, and the R rating is a bit lower than fibreglass too.

 

[AlterEgo]

the heat trap issue is affected by several variables.

including, the mode of heat entry into the house, its materials, orientation and roof/ceiling/wall characteristics.

concentrating on the roof, prevention of heat ingress in the day is good, but IMO, on hot summer nights, simple physics demand that heat will be trapped, therefore, your house will cool down much slower on very hot nights.

It has proven to be the case here.

I have fully deducted aircon, and spoilt teenagers who demand aircon at night if it is too hot

If anyone can convince you (or me), that you wont be hotter on a hot summer night, well I would like to hear how that can be.

Surprise, Surprise, they never mention this issue on the TV ads

Winter should save money.

Some people cant stand hot nights, if you have no aircon, to be borne in mind

pps BEPPA profits today alone payed my cladding bill several times over

I've found the same thing. I need to run the air-con at night during summer (I'm in Queensland), which wasn't as neccessary without the insulation, however the air-con gets used less in the day than it did without the insulation.

 

[moXJO]

the heat trap issue is affected by several variables.

including, the mode of heat entry into the house, its materials, orientation and roof/ceiling/wall characteristics.

concentrating on the roof, prevention of heat ingress in the day is good, but IMO, on hot summer nights, simple physics demand that heat will be trapped, therefore, your house will cool down much slower on very hot nights.

It has proven to be the case here.

I have fully deducted aircon, and spoilt teenagers who demand aircon at night if it is too hot

If anyone can convince you (or me), that you wont be hotter on a hot summer night, well I would like to hear how that can be.

Yeah, unless your house has EPS cladding, which is basically 80mm thick rendered foam walls your outa luck. My parents have it on their house and it’s like living in an esky temperature is always pretty constant.
Hot summer nights can be made worse by kitchen heat (exhaust fan in kitchen?), having doors and windows open while aircon is running and probably a lot of other stuff.

Having tiles on your roof means they could hold the heat for a lot longer than tin. Which won't help on those hot nights.
If you are building a home, its good to look at these types of issues beforehand

 

[dalek]

Polyester batts are more expensive and have slightly less thermal value that glass wool so you need to specify higher R values if installing polyester.
Glass wool is no longer fibreglass, hasn't been for some time.
The issue with F/glass was the solubility of fibres in the lungs, which is not a problem these days although some people can be allergic to almost anything.

The loose blow-in style product has a tendency to settle over time and should not be considered IMO.
While most regions are adequately served by R3.5 batts if you are in a region that suffers temperature extremes, e.g. A.C.T. then R4.0 would be the choice.
Lots of windows will have significant impact on thermal performance and you need to ensure blinds / curtains are used to get best results.

While you will get positive resuts in hot weather the most noticable improvements will be in cold conditions with a comensurate reduction in heating bills.
There really is not much to debate, the cost /benefit analysis is excellent and the improved comfort is great.
Just make sure any downlights are given plenty of clearance when installing the stuff.

 

[jackson8]

Gary, thank you. Why are you opposed to the polyester?

as mentioned by another it is more expensive to acheive the same R. rating also polyester is used as a sound proofing material as it is a denser material

you would be well advised to check out the ignition point spec. for anything that you may be considering

 

[Smurf1976]

Been involved with this one plenty of times...

Personally I'd go for glass wool batts as the cheapest and most effective solution. They won't settle or otherwise wear out - they should last as long as the house. It won't set the roof on fire and it doesn't make an attractive nest for pests (though rats especially will nest just about anywhere). And they're also usually the cheapest option as well.

Everything else has problems. Cellulose (blown in), wool, foam and polyester are not inherently fire proof.

Your wool jumper might be fairly safe to wear if there's a fire, but low density batts in the roof sure aren't. Same with the shredded newspaper etc. It's fine when they do the demo with it packed as dense as they can get it. But coal or wood don't burn under those conditions either. Pack it loosely as its intended to be installed and it's an entirely different story when the blow torch is applied unless the manufactuer really has done the fire retardant treatment properly (and plenty don't).

Polyester is better than the rest, but it still doesn't have the inherent fire proofing of glass wool. I'd be a lot happier with polyester or foam than wool or shredded newspaper though, but in terms of fire safety I'd still rather have glass wool or rock wool.

Why the concern about fires? Let's see... Wiring, light fittings, heater flues, sparks under the eaves during a bushfire. Lots of ways a fire can start in the roof with or without insulation. If you're going to put something up there, then having something that won't burn makes sense to me.

Another problem with the blown in types is they move about and/or settle over time and this greatly reduces effectiveness. It can be manufactured and installed well with fire retardents and a sealing spray. Do that and there's not much to worry about and yes it will work. But I've seen plenty of situations where that isn't the case...

As for foil, well that's in a completely different category to the rest since it's a reflector of radiant heat. It does some good, especially for keeping the heat out if installed directly under the tiles / tin when the roof is installed. But in my opinion it's not as good for keeping the heat in as the other types of insulation. It's still better than nothing, but batts will keep you warmer in winter.

Regarding the heat trap in summer issue, that's only true if the indoor temperature is above both the desired temperature and the actual outdoor temperature AND you don't have a lot of ventilation. If you ran a properly sized air-conditioner all the time (not that I'm saying you should) then it wouldn't be an issue - adding the insulation would simply alter the tmes the A/C runs and reduce its overall running hours and cost. If you had a window open and a decent airflow then there just shouldn't be a problem assuming it's not hot outside at night. And if it is hot outside, then you'd need the A/C on anyway...

I'm sitting in a house that's 8 degrees warmer than it is outside right now. I guarantee you that if I open the windows at each end then the inside temp will drop to near the outside temp in a matter of minutes. That applies regardless of the actual temperatures. But I do know about that problem in a situation with a lack of ventilation - but then most houses do have windows.

Main thing if you want to stop the house turning into a greenhouse is to make sure it's not a greenhouse to start with. Sun shining in closed windows is going to heat the place up, adding insulation merely increases the effect. Awnings etc are the solution to that problem.

If I were you, I'd be insulating with glass wool batts. Just to make sure everything's safe though, downlights must not be covered (this is the law) no matter what sort of insulation is installed.

 

[Julia]

Smurf, thank you for very comprehensive comments, as always.
And thanks to everyone who has given their views. It's very helpful.

 

[moXJO]

Been involved with this one plenty of times...


As for foil, well that's in a completely different category to the rest since it's a reflector of radiant heat. It does some good, especially for keeping the heat out if installed directly under the tiles / tin when the roof is installed. But in my opinion it's not as good for keeping the heat in as the other types of insulation. It's still better than nothing, but batts will keep you warmer in winter.

.

To get it under the tiles on an existing roof you more or less have to re-roof the entire house(pull old tiles off and then re-lay them). It’s a massive job and not worth the cost. Same for tin roof

 

[awg]

Been involved with this one plenty of times...



Regarding the heat trap in summer issue, that's only true if the indoor temperature is above both the desired temperature and the actual outdoor temperature AND you don't have a lot of ventilation. If you ran a properly sized air-conditioner all the time (not that I'm saying you should) then it wouldn't be an issue - adding the insulation would simply alter the tmes the A/C runs and reduce its overall running hours and cost. If you had a window open and a decent airflow then there just shouldn't be a problem assuming it's not hot outside at night. And if it is hot outside, then you'd need the A/C on anyway...

I'm sitting in a house that's 8 degrees warmer than it is outside right now. I guarantee you that if I open the windows at each end then the inside temp will drop to near the outside temp in a matter of minutes. That applies regardless of the actual temperatures. But I do know about that problem in a situation with a lack of ventilation - but then most houses do have windows.

Main thing if you want to stop the house turning into a greenhouse is to make sure it's not a greenhouse to start with. Sun shining in closed windows is going to heat the place up, adding insulation merely increases the effect. Awnings etc are the solution to that problem.

If I were you, I'd be insulating with glass wool batts. Just to make sure everything's safe though, downlights must not be covered (this is the law) no matter what sort of insulation is installed.

Very true.

I am almost passionate about passive solar design.

In the ideal circumstance, with correct axial orientation of the house on block, eave width, window placement, construction material, insulation and a simple but optimised ventilation, plus a few other cheap tricks, the need for any heating or cooling can be vastly reduced in most areas of Oz.

Its a real shame more is not made of it, its world saving stuff.

Add solar,recycling, permaculture etc and I'm sure one could halve individual energy consumption in 20yrs

accurate in what u say about inside vs outside temps....if u have traffic noise however, we keep the windows shut at night..big dif in temp

 

[Smurf1976]

To get it under the tiles on an existing roof you more or less have to re-roof the entire house(pull old tiles off and then re-lay them). It’s a massive job and not worth the cost. Same for tin roof

Agreed. It's really only an option in a new building or if the roof is replaced, but it's worthwhile if you do want to keep the heat out.

Consider if you've got a black tin roof of, say, 150m2. The sun shining on that at mid day is equivalent to running electric 60 fan heaters running flat out which is rather a lot of heat. Go into the roof space and, well, let's just say you'd better like it hot.

Consider that a typical solar water heater only has 6m2 of panels which is tiny compared to the roof area. But that small area is more than enough to heat all the hot water the house is likely to use during sunny conditions.

A light coloured roof will reflect much of that heat. I did an experiment on a garden shed with one area painted black, the other white. The white area was slightly warm (about 20 degrees outside and clear sky). The black area was too hot to comfortably touch.

Keeping the heat in, as opposed to out, is a somewhat different scenario since the radiated heat isn't really such an issue. By the nature of wanting to keep the heat in, there generally isn't much sun to start with. To keep the heat in, just insulate everything you can. The more the better, although above about R4 the financials won't be so good and there's a limit to how much insulation it's practical to fit in any given space.

Qld - Try and keep the heat out. Ceiling insulation will help but so will awnings, foil and anything else that keeps the sun out. If the house is like an oven during the day due to the sun shining in and you don't have air-conditioning, then that's when insulation could make things worse at night.

Tas - Just insulate the lot. In the rare event that it's actually hot at night, well there's an opportunity to run the heat pump in cooling mode (which helps clean it out by the way). And I think most would rather be hot 2 nights a year than freezing all through winter anyway.

SA - Ideally you want to keep it out in Summer and keep it in during Winter. Insulate and, during Summer, have some means of keeping the sun out (awnings, shutters etc).