Insulation under custom orb roof brisbane

[damian]

Hi all,

I have a question. I have some general knowledge on insulation, what I am looking for is specific recommendations for my specific problem.

I live in a tiny 45 sqm house built in the late 1800's. I'd put a bulldozer through it but unfortunately it's heritage listed. I'm west of brisbane on the west side of a mountain and the place is VERY hot. In summer I can achieve a small amount of thermal lag by keeping the place closed up in the morning, but by late morning inside temperatures are as high as outside.

The house has a high pitched single pitch/belcon roof. The block faces north east so the front pitch gets the morning sun and the rear pitch cops the afternoon sun. Currently it is clad in rusty gal custom orb which is very second hand.

Now I don't need another job on my list, which is already infinitely long. At this rate I won't be allowed to die until I'm well over 200 years old. I thought however that re cladding in a lighter colorbond colour and laying some foil insulation under it might help drop my temps.

Understand that cold is NOT a problem. It hardly ever gets cold enough to warrant a jumper let alone anything else. The problem is excluding heat from the house.

The problem is I am a bit baffled by the array of foil insulation products and don't really know what I can expect in terms of temperature reductions.

So can anyone enlighten me?

Thank you very much for reading.

[Fuzzie]

I have no quantitative answers but my story might give you some qualitative idea. Our current house, facing pretty much due north, has a low pitch roof. It was originally Decramastic Titles (those horrid tin things covered in bitumen and small gravel, [looks away and spits]). Anyway the last owner painted the house for sale a sort of ochre yellow colour with a black roof. The black painted tin roof turned the whole place into a quite efficient solar oven.

I attempted to put some insulation in the ceiling space after we moved in. Two problems, it was summer and the with the low pitch I didn't have enough room to move around in the ceiling space to place insulation batts. I did get some packs of batts through the manhole but after being there for a few minutes (I never put a thermometer in there so don't know the actual temp it got to) I just about passed out. I managed to crawl out of the roof space and fall into the pool fully clothed and must stayed there for a very long time until my core temp dropped to something reasonable.

Following that aborted attempt to insulate we engaged professional roof replacement. We went with cream colourbond metal decking and since I already had the batts for ceiling insulation asked for just plain sarking under the decking. The installers spread around my batts on the ceilings while doing the decking. You could monitor what part of the roof they were working on by simply walking in the rooms underneath. The indoor temp drop was instant.

I had the option of getting foil blanket rather than simply sarking at the time of installation, but because I already had the batts and I was low on funds at the time, I saved only a few $ by using simple sarking foil.

I can now get into the roof space in summer and it is still a reasonable temp. Hot but reasonable, it wouldn't kill me anymore. If I did it again I would get the all in one sarking and insulation blanket installed under the decking. After seeing the water damage done to houses simply after whirlybird roof vents blew off during a cyclone, I wouldn't put one on my roof in an attempt to ventilate the roof space.

When I'm driving around new housing areas in SEQ these days I only wonder about the vagueries of decorator fashion and why people put dark coloured colourbond roofs on their houses. It''s like cars, why anybody in Qld would buy a black car is beyond me. Go light colour with insulated blanket foil.

Hope this helps.

[Chris Parks]

Consider solar fans to change the air in the roof space.

[damian]

When I'm driving around new housing areas in SEQ these days I only wonder about the vagueries of decorator fashion and why people put dark coloured colourbond roofs on their houses. It''s like cars, why anybody in Qld would buy a black car is beyond me. Go light colour with insulated blanket foil.

Hope this helps.

Thank you for the reply.

I actually bought a black car brand new in 09 but I do see your point. I too have wondered about people doing dark colour schemes in qld. I understand the victorians doing it but up here it's madness.

I expect the light roof and foil insulation will do something I was rather hoping for some independent advice/experience on how big a difference it will make.

I happen to have a brand new whirlybird I bought years ago for the house but never installed it. I put 2 on the shed and it made a measurable difference but not the sort of difference I'd hope for spending $1600 re roofing. Some of the ebay sellers claim about 7 or 8 degrees, that would make me very happy but I'm not sure it's realistic. Combining it with venting the roof is another can of worms. I'm inclined to do either or not both.

Anyway suffering 36 degrees today. The heat up here is entirely different to down south. When I lived in sydney it could be 45 outside and I'd be mowing, walking etc no bother at all. Up here at 30 I'm like a goldfish out of water, gasping for air.

[damian]

Argh. I've spent much of today reading forums. Religious wars everywhere. Sigh.

[Beardy]

Is there a particular reason you only want to do foil and not an insulated blanket which is the standard practice for housing and then batts on top of the ceiling
The foil is more the cheap option for sheds where it also helps for condensation but is not as good as an insulated blanket

[Fuzzie]

Is there a particular reason you only want to do foil and not an insulated blanket which is the standard practice for housing and then batts on top of the ceiling
The foil is more the cheap option for sheds where it also helps for condensation but is not as good as an insulated blanket

I think that's a question for me not the OP

I did it because of the budget available at the time. I was recounting my experience that the combination of light coloured colourbond plus sarking alone was still quite effective.

[rod1949]

Use a product called anticon. It is reflective foil on insulation blanket. It goes imediately under the corrugated iron and over the top of the purlin. The foil side is on the underside thus it supports the insulation from deteriorating. The anticon also helps eliminate the bang of the corrugated iron due to the expansion and contraction (heating and cooling) of the corrugated iron. Then lay thick insulation batts inbetween the ceiling rafters. You will notice a dramatic difference.

[damian]

Good question. I wasn't ruling out anything but because of the way my house is built I can't lay batts on the ceiling. I can explain if you care, house was built in the 1800's...

I wasn't planning to use plain foil. I've looked at the earthwool space blanket, anticon, ametalin and the kingspan product and others. Prices vary a lot and it is not at all clear to me how their performance compares. I've ruled out the ebay bubble stuff. It is probably chinese and may not be approved for use in australian homes. It may even present a fire risk in queensland temperatures. The problem with foil blanket products is it's not just R values, you have to factor emissivity and installation.

I am amazed at the religious wars around roof ventilation and paints. Most of it is ignorant rants and trawling through the rubbish to find useful information was exhausting. It has however got me thinking about refinishing the existing roof. Once I've mulled everything over I'll post here what I have found in case someone in future has a similar issue but I'm still digesting it all. Reading other forums really makes you appreciate they happy friendly places like this one.

If anyone has any actual qualitative experience I would love to hear about it.

[elver]

Damian,

I installed air cell in two houses in lismore. Same problem and Similar climate to you - pre 1900 houses, tin roofs, no insulation, with crazy hot and wet air in summer.
Installing on NY day stapling to the underside of the rafters my family could tell which room I’d done within minutes. Went from oven to bearable with a fan on.

Worth every cent.

The only downside was in winter the houses took a while to warm up. There were massive losses of heat out of the ceilings and floors and no heat load from the roof anymore to warm it up.

I trialed sarking alone. It was about half as effective as the air cell, and harder to install as retrofit.

If I was re installing the roof sheets I’d use anticon like I did in my shed, but for retrofit aircell is great. Just make sure you don’t electrocute yourself like those poor backpackers.

[elver]

Forgot to add - aircell is good to retrofit because it’s a bit stiff. Makes installing by one person ok, and tapping joins and seams do able

On my current house I installed foam backed silver stuff on one veranda and air cell on the other. Both installed to spec when putting tin sheets on. The aircell is considerably cooler - far less radiant heat on my balding head!

[damian]

Thank you so very much for that, exactly the sort of first hand information I've been looking for.

I have a plan.

The custom orb I found cheap is listed as white/beige. It should be highly reflective. My ridge runs left to right so the neighbours won't see it at all and there are no houses above me. I'm planning to call them monday confirm availability and go pick it up. About $750 will do the main pitch.

I've ordered a couple of indoor outdoor thermometers on ebay. When they arrive I'll get some base measurements, then fit new roof with insulation under and remeasure.

Because I'm fitting new steel I'll have options due to improved access to the cavities. I can't get at any of it from underneath.

Cold is not a problem, it basically never gets cold at my place. We would get maybe 7 days a year when I put on a jumper.

Thank you for the recommendation on insulation. My neighbour is a builder and he uses glass blanket with foil backing. I'll decind on the insulation when I get closer to the installation.

Today I got up there with the waterblaster and cleaned the roof and gutters. The sheets are pretty shot so I might as well replace them no matter what.

[Fuzzie]

Damian, a word of caution. You say the property is Heritage Listed. It would probably be advisable to make some enquiries about what if any restrictions may exist regarding colour schemes allowed for renovation/repair before you commit $s.

Cheers,

[Beardy]

Damian, a word of caution. You say the property is Heritage Listed. It would probably be advisable to make some enquiries about what if any restrictions may exist regarding colour schemes allowed for renovation/repair before you commit $s.

Cheers,

A valid point, be careful not to draw undue attention to your property or you might find council with their heritage architect on your doorstep
If it currently has galv sheeting I would be sticking with that and maintaining its character

Another point to consider is if you have lead flashing on your existing roof it is not compatible with colourbond

[damian]

No lead.

I read over the heritage regs and I don't think it will be a problem. They say tek screws are ok and colour schemes should be in keeping. House is white with cottage green trim so white corro and I'm considering a cottage green ridge.

You would think they would be grateful I'm replacing the rusty and shot old roof but of course the idiots minds don't work like that.

I have been spending sometime probing. I've never looked inside the roof so decided to lift a couple of sheets and measure the structure. It was a lot better than I expected. Rafter 100x50, perlin 35x75, ceiling batten 25x50. There is more structure in the cavity section than I thought as well.