termite
Member
The roof joists are not exposed - they are between the gyprock ceiling and the sisal/battens-that-the-tiles-sit-on.
I've been reading about Foil Board. It might just do it! I'll need to see what is to be done about the downlights, but its rigidity should make it easy to slide under the tiles without snagging. And the quoted R-value for that looks impressive.
matas
Member
But, if the joists (rafters) are not exposed, then you do have a cavity, between the gyprock and sisal (the thickness of the joists).
Wouldn't it be easiest and most effective, by far, just to lift a few tiles, cut the sasal a bit, and push soft fibreglass batts down along the cavities, between the joists ?
You could cover reasonable areas with each hole.
Then just tape up or reseal the sisal, if you want.
termite
Member
Yes, there is some sort of cavity, but not enough for the usual batts (perhaps 100mm?). I've already attempted to get a quote for standard batts - they said 'not possible'. Of course, they may not be aware of all ways to install insulation, but it's a bit harder to discuss things when you're interstate and the RE rental agency is managing the process. I also note that others have commented that batts won't 'push' down the gap as they snag on little protrusions.
Plus there is the issue of wiring and the downlights, which are not (yet) fluorescent or LED. There needs to be an adequate gap around them.
I've seen one comment today on another forum, from someone who tried to use Foil Board to insulate their floors, and found problems with it (moisture+didn't work), but that doesn't say it won't work on a roof.
Even at the worst, the cost of pulling off the tiles, installing Foil Board and re-laying the sarking and tiles is still cheaper than increasing the thickness of the roof by 100-200mm - with the added benefit that the clerestory windows won't be obscured by the new roof line.
I had initially considered air-cell foil sheeting because of its thinness, but it seemed to be better at keeping heat out rather than keeping it in, and its effectiveness is reduced by dirt settling on the top. This Foil Board is similarly compact, and its polystyrene core is covered, reducing any vapour emission. The difference is in its two-way effectiveness and reduced reliance on the surface reflectivity.
Then there's SuperTherm ceramic paint that I'm now going to investigate...
given your stated budget (6 figure )...
depending on the age /condition of the roof tiles I would contemplate replacing the roof tiles (possibly with colourbond cladding, installing insulation ,improved ventilation , increased eaves ,especially over clerestory windows and other roof upgrades all at once.
but without seeing the house ,hard to say.
spending money on fixing the roof is money well spent IMHO.
also helps preserve the rest of the house for decades to come.
Roofs are very neglected in most houses.
Of course there are many other factors to consider when contemplating changing from tiles to metal cladding (tiedown being an important one ).
matas
Member
I personally would try to make use of the cavity between the roof joists, for insulation.
If its like my roof, the joists will be a lot deeper than 100mm (mine are 190mm).
While my tile battens are only 25mm thick.
The foilbard retrofit for cathedral ceilings, suggests tile battens 75mm deep, giving a 25mm airgap above and below the 25mm thick foilboard.
Though 25mm foilboard put between 25mm battens, without an air gap, should still insulate to some degree.
What about spray foam polyurethane insulation ?
It is good for awkward spaces, with small access.
And also replace the lights with low energy, low heat types.
termite
Member
IF the joists are deep enough...
I wonder if they could:
* Take rows of roof tiles off at the top and bottom of where a Foil Board panel would sit
* Cut back the sisal to expose the joists
* Nail supporting brackets halfway up the sides of the joists, each side of the board, top and bottom
* Cut Foil Boards to fit the joist gap width
* Slide Foil Boards from the top down through the cuts in the sisal, to rest on the brackets.
* Tape up the cuts in the sisal
* Replace the roof tiles
Does that seem practical?
I don't know how much SuperTherm costs, but boosting the Foil Boards' performance with a layer of ceramic paint either side seems like my kind of excess.
Matas is right; it is simple to replace the type of downlights, though I was waiting for LED technology to mature further; there is some serious wattage there. Is there anything else that will give the brilliant 'twinkle' that halogens offer?
To dave lawrence; I am still debating whether to eventually replace the roof with terracotta tiles or Colourbond. The house style isn't strong either way, though at one stage I considered a Mediterranean look. I am also worried about losing the flexibility to easily make small roof changes with the Colourbond. As there is no north-facing 'plane', I also wanted to change the line to create a platform suitable for eventual PV panels. Is there a discussion topic already for roof material choice? It seems like there should already be one.
sounds like you are contemplating serious changes . good. take your time. i say to all people about to renovate you either need lots of time or lots of money... most people don't have both .
i have been teaching energy efficient design for 12 years and the best advice i can give is to prioritize what you are trying to achieve with what you can afford to spend . write that down ,show your partner and thrash it out with them before going any further.
you will be amazed how two people can differ in their priorities . that in itself is normal .. the trick is finding a compromise . the design part is easy (relatively ) once you have really worked out the brief of needs and wants.
good luck . if you start a topic on roof materials i shall throw my 10 cents worth in !!!
as for the lack of north facing plane ,if you address all the issues mentioned above in your brief (ie. needs and wants, priorities aesthetics vs function etc etc ) then the answer will become apparent to you .
matas
Member
I think it is a very good idea to try to put cut polystyrene boards (EPS), between the joists.
If you start from the roof peak, and feed them down, with the help of gravity, you could probably get them down a long way (assuming the joists are fairly parrallel).
And maybe not even have to cut the sisal much.
You could temporarily remove light fittings, or work around them.
But I personally would probably omit the wooden support brackets for the EPS board - much too fiddly and difficult.
What about just laying the EPS on the plaster.
Surely that would still insulate very well, with the no air gap below the EPS (and is condensation really significant here ?)
Also I would think about using standard EPS board 100mm thick.
Its available from many places and is a lot cheaper than proprietary products, like foilboard.
http://buybuildingsupplies.com.au/polystyrene-sheets-foam-sheets-c-22_2580_2581.html
I'm guessing half the price and twice as thick.
As for the reflective foil on top, many have said that in a roof situation, it is quickly covered in dust and ineffective.
But these are just my opinions, and it would be best to get second expert opinions, and maybe try a test area.
termite
Member
Thanks for the help with economising, both in product and installation.
I just asked Mr Google for web reference to the R values I might be able to achieve with different thicknesses of polystyrene/EPS.
Wikipedia gave a rating of R4.20/inch.
http://rvalue.net/ rated it at R4.00/inch.
http://www.roofhelp.com/Rvalue.htm rated it at R3.85/inch.
That doesn't seem right; Foil Board was not claiming nearly that. This disparity does make it difficult to compare apples with apples.
The next question will be who is classified as an 'expert' for a second opinion...
Thanks, all.
matas
Member
The Foilboard literature uses metric SI units,
but when they claim R2.5 for for a cathedral ceiling with 25mm foilboard,
that is for the "Total building system" which includes ceiling liner, tiles - everything in the roof.
You can't compare that to 100mm of EPS at R0.65 per 25mm (Wikipedia)
Basically Foilboard is 25mm EPS with some foil stuck to it.
I am guessing that 100mm of standard EPS would insulate better than 25mm foilboard, and be cheaper.
Re: US R-values
It is ironic that Americans have to calculate in British Thermal Units to compare insulation results.
I was astonished at their amazing success with insulation until I realised you have to divide by six.
cool at home
Member
A friend is about to replace their tiles on cathedral roof with Colourbond, and (on my recommendation) planned to take the opportunity to install good insulation - Air-cell (R2.7) plus batts appropriate to the space available (approx R3.0). His builder has baulked at this, saying Aircell will lead to condensation in the roof space and that 'builders blanket' (not sarking??) should be used instead with R4 batts.
There are no exhaust fans into or through the ceiling and roof, so unless the roof leaks I can't see why condensation would get into the space... although I agree that Air-cell properly installed does provide pretty tight coverage that could (probably would) be a problem with (say) a bathroom exhaust fan.
And the space is 200mm, which I think is pretty narrow for R4.0 batts.
My friend is also looking at reflective coating or light coloured colourbond.
My experience is that heat in summer is a major issue with cathedral ceilings and excellent reflective insulation is essential.
Has anyone had good or bad experiences with Aircell in cathedral ceilings, and/or able to recommend an alternative reflective product suitable for the job. House is in Sydney.
Many thanks
Susan
Paul Denton
Member
Susan
As a long suffering Cathedral roof dweller, going colourbond and choosing a light colour (surfmist is the lightest) will go a long way to keeping the heat out. I have painted my roof in an effort to reduce the pain of Perth summer heat (48 degrees outside means about 30 degrees inside with aircon at full blast). since painting my roof a lighter colour,(with Solareflect paint, colour surfmist) temperature readings on the underside of the metal after painting has given me a 17 degree reduction down to the ambiant air temperature.
As for insulation, aircell iteslf is not a good insulator on its own,(check the manufacturers website and look for the 6 point font hidden at the bottom) but when correctly installed and in combination with the other building components it is the sealing of the air space and the trapping of air that makes it work. If you have a 200mm space available then you are doing alot better than the 90mm I have. R4 Batts might be overkill for Sydney, so a thinner R2.5 or 3.0 might do. also, make sure there is a an air space left in the roof otherwise the tin heats the batts, the batts heat the celing boards and after a few days of summer the whole roof acts as a fantastic heat bank. Vent all wet areas to the outside.
Paul
Paul Denton
Member
Susan
another option is to look at something like semi structural panels that hav einbuilt insulation coveriong and underside , e.g. solarspan type products http://www.solarspan.com.au/solarspan/resi/technical.html
also, the best solution really depends if the desired outcome is trying keeping warm in winter or cool in summer, in my case cool in summer so I want to reflect as much heat as possible. I was forgetting Sydney can get quite cold so you might be wanting to go for keeping heat in.
cool at home
Member
Thanks for both your posts Paul... I have passed on your comments.
Although it does get cold in winter, summer is still most households most difficult problem in Sydney.
Re the Air-cell need for excellent sealing, you have got me thinking...
I have Air cell (plus batts) in my tiled attic roof, with Air-cell under the roof beams, retrofitted, and sarking above the roof beams, done at time of building. Frankly I don't have a lot of faith in the builder we used, so not sure how well the original insulation/sarking was done, but we used a very reputable installer to do the Air-cell recently. My question is, we have 2 Supavents on the roof, primarily to let out condensation in the ceiling as our bathrooms vent into the attic. While the Aircell is carefully sealed at all joins, where the Supavents are a simple cross was cut into the Aircell, which was folded back and taped lightly to keep the hole open - allowing us to seal the vents at a later time. WE had mentioned to the installer that we are not keen on the Supavents and - when we can afford to - at some time in the future will duct the bathroom vents to the exterior and close the roof space back up. As these Supavents gaps are breaks in the otherwise well sealed Aircell, are they likely to severely undermine its' performance?
Thanks
Susan
Paul Denton
Member
Susan,
the air-cell under the beams in the attic roof sounds like a standard method retro-fit so okay so far as it goes.
As for vents, I would go for connecting the bathrooms direct to the outside as soon as possible. As for the current slits, what is most likely to happen is that you still get a good insulation performance for the roof itself (tile/sarking/aircell) but are leaking a lot of air in and out of you roof space it self. While you always want a bit of ventilation in the roof space, you now appear to have a lot more, which may not help in keeping the heat out next summer.
cool at home
Member
Many thanks for all your input Paul. 'Tis much appreciated
Susan
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Foilboard
Member
Matas,
My name is Ryan and I am the National Sales Manager and Technical Advisor for Foilboard Australia P/L. I hope that I may be able to provide some feedback on the apparent dust film build up on RFL's and subsequent degradation of foil emittance degradation.
Comments below were from R & D Services P/L (David Yarbrough) March 2010;
The region between the roofline and the reflective insulation typically form an enclosed reflective airspace. In some rare occasions, there may be some negligible airflow through this enclosed RFL cavity. As a result, an accumulation of dust or other contaminants is very unlikely to occur. In the absence of definitive data to the contrary, an arbitrary increase in surface emittance due to contamination is not justified.
*******
With regard to Foilboard (Foilboard Insulation Panel), it is important to note that all Reflective Foil Laminates should not be considered the same. All have different levels of emissivity (materials ability to reflect radiant heat) and subsequently have a huge impact on the total system value. Foilboards emissivity values for both RFL and anti glare sides have been tested by the CSIRO with values of 0.03 and 0.038 respectively, even lower with other NATA accredited authorities.
Furthermore, the Foilboard Insulation Panel has 20 Microns of pure aluminium foil directly laminated to the SL grade fire retardant EPS core making it totally impervious to moisture and delamination.
There needs to be a governing authority to weed out non compliant materials on the market (both RFL and bulk) as it is such a critical aspect to long term sustainable construction.
Ryan
foam insulation
Member
This is a great thread, I'm sure that using some foam insulation will help. It can be put between the walls in small spaces 50mm thick, I believe. Hopefully this helps. It also has the R value of about 2 [metric].
Foilboard wrote:
There needs to be a governing authority to weed out non compliant materials on the market (both RFL and bulk) as it is such a critical aspect to long term sustainable construction.
Interesting to read the above comment; it would appear that non compliant products are also a scourge in this industry. As with non compliant products in other industries, the government and regulating bodies most often fail to act in the public's interest and the excuse used is that while some products are non compliant once fitted, their sale most often is not illegal.
It is also 'conviently' overlooked by the powers that be that many such products are the recipient of generous government rebates in addition to the false claims that often accompany such products.
I share Foilboard's frustration.
kate
Member
about the cathedral ceilings, exposed rafters. i am not worried about losing the effect, I am going to cover mine with gyprock to keep out the dirt and insects that love old tiled roofs. and i want to insulate at the same time to keep out the heat. so, I was going to do just batts.i think i have (rafters, plyboards, maybe old silver backed sarking, battens, cement tiles.
after reading all your great suggestions, i was going to do foil plus batts, but am confused. csr is wrong, i have ceiling full of ants and dirt, which drops though the ply/rafter gaps into the room. this would cover the foil insulation. what should i do.
does the person wanting to redo the outside of the roof know that it is cheap and easy for a builde to batten and gyprock the rafters, and install insulation inth gaps between the rafters at the same time. would be cheaper to pull of old gyprock than rebuild metal roof.
Buzzman
Member
kate
Sounds like you have an ant problem. Deal with that first.
Adding insulation batts as the gyprock ceiling is tacked over the rafters is the way to go. Simple, easy, relatively cheap.
But if gyprock is in place, it will be cheaper to pull up exsting roofing, addd batts and then sarking, reaffix old battens, replace roofing.
Only new materials are insulation, everything else is re-used existing. Labour is only expense, and lifting corrugated iron is easy enough for a handyman to do - just need a hex head bit for the battery drill.
Gyprock, while cheap as a material, requires a lot of expensive time finishing it off - especially joints which normally need two goes to get smooth, and then needs two coats of paint as well.
It SOUNDS harder but is actually easier to take of the roof, not the ceiling.
ghostgum
Member
kate,
There are two sides to foil insulation. One side reflects heat. The other side poorly radiates it. So even if there is dust on the top surface, the shiny bottom surface should remain clean. You need to leave an air gap betwen the foil and the insulation below of at least 25mm. If they make contact, then you lose the advantage of the foil/radiant barrier.
Two layers of foil isn't twice as good as one. If you have one layer already, then adding another won't make much difference.
Wayne Kotzur
Member
Regarding potential moisture buildup with foil barriers and celing vented exhaust fans I note that Aircell do make a 4mm floor use foil laminate (R0.12)that is air permeable (lots of tiny holes) rather than the thermal break 6.5mm product(R0.2)which may reduce worry. They are about twice as efficient at keeping heat out as holding heat in. Anyone who has pulled a low sloped roof will know how dirty the sisalation gets with dust dirt & nests etc. The steeper the roof and the less open the roof to the air the cleaner it will keep. If you are relying on foil only then pehars a cheap sisalation above with the appropriate 25-30mm air gap will help keep it clean and give you two good air gaps
Ben1
Member
I am also investigating insulation for closing in an exposed rafter cathedral ceiling. The rafters are 245mm deep, so I am thinking of using R5.0 (210mm) fibreglass batts with RFL of some kind sitting on top of the batts (giving a 35mm air gap between the top of the insulation and the existing ceiling lining boards). My question is: is this the best insulation combination? What sort of RFL should I use?
Buzzman
Member
Ben1
Can we assume form your description that the "existing ceiling lining boards" are on top of the rafters?
If you do not intend to remove the roof, then you will have to put RFL underneath the ceiling lining boards, so a film which can be glued to that surface would probably be easier to cut and fit.
With 245mm depth to the rafters there is ample space for 150mm R5 batts. Plus a 30mm air gap above them = 180mm.
You will need to install a false ceiling to support the batts, and fibro or ply or similar board is the easiest and cheapest way.
Simply attach 25 X 25mm battens 55mm up from and parallel to the lower edge of the rafters. Cut board ceiling to width between rafters and slip it up and in to rest atop these battens.
Slide pre-cut to size insulation batts down into the space thus created.
The 'last' one on each row run some fabric strips above the batt to hold the batt down onto the ceiling panel as it is being installed, then once ceiling dropped into place, pull down gently on strip to ensure batt sits down on ceiling no up agains old cailing, then carefully remove fabric strips for re-use on next row.
Sounds complicated but easy once you've done it once. 
