Alternative Technology Assn Forums

1. 

   wlb
   Member

   Just wondering if anyone has any ideas to toss in here.

   The house is a simple rectangle with a very shallow pitch (7 degrees) gable roof.
   Exposed Oregon beams with pine lining boards nailed to the top edges of the beams to form the ceiling.
   70mm battens nailed to the tops of the lining boards with Custom Orb Zincalume nailed to the battens.
   A 70mm roof cavity with no access.
   Fibreglass bats laid between the battens, but the battens are further apart than the width of the bats and that gap has been left empty. I only discovered this when I removed the barge board flashing at one end to fix a problem. So quite unsatisfactory.

   I need to re-insulate the roof properly, but this can only be done be removing the roofing iron.

   The easiest but least satisfactory solution is to remove a few sheets at a time and fill the gaps with pieces of new bats.

   The next option is as above, but to replace all the bats with the best 70mm thick insulation available.

   The last and most difficult option is to remove the sheets, increase the thickness of the battens (or add another on top) so as to increase cavity depth beyond 70mm, and add new insulation in the gaps and on top of what is already there.
   This will of course necessitate changes to the fascia and deeper flashing at the barge boards.
   And the way the weather is these days, it may even be advisable to have temporary flashing on hand so that the roof can be made weatherproof if the job is only partially done before rain arrives.

   Posted Tuesday 1 Dec 2015 @ 4:26:00 am from IP #
2. 

   axess
   Member

   wlb

   Do you plan to do the roof yourself or get contractors in?

   Posted Tuesday 1 Dec 2015 @ 6:57:39 am from IP #
3. 

   johnmath
   Member

   What region are you in wlb? If it is anywhere that gets hot (>35), I would strongly recommend increasing the distance between roof cladding and ceiling so that you can fit in reflective foil sarking with air-gaps and thermal breaks on both sides of the foil, and R5 or greater batts.

   You could even add another roof cladding surface, leaving the existing one in place, to create the space.

   Low pitch roofs absorb more heat than steeper pitches where some radiation 'glances' off, so you are at a disadvantage to start with.

   If you are in a cold climate, maybe you could fill in the gaps between the beams and add another ceiling treatment below. Just bear in mind that cramming bulk insulation into a small space and compressing it reduces its R rating. Bulk insulation needs to be 'fluffed up' to achieve its R rating, just like the doona on your bed.

   Posted Tuesday 1 Dec 2015 @ 7:16:19 am from IP #
4. 

   Annette
   Member

   70mm is not much room for insulation. You might also be surprised how much raising the roof will cost if you are hiring someone to do it.

   I suggest adding batts underneath the existing ceiling and adding a new ceiling underneath. Of course, you have to check that you have enough height (2.4m) to stay within the NCC (BCA) rules for minimum ceiling height.

   The advantage of doing it this way, is that you can start with the living rooms and see what difference it makes.

   Posted Tuesday 1 Dec 2015 @ 10:52:28 am from IP #
5. 

   tezz
   Member

   Weeks ago I saw a website that offered a product of new corrugated roofing, as well as insulation that was fixed over the top of the existing sheets.
   As I only briefly scanned it, didn't delve any deeper, nor did I bookmark. Now I can't re-find the site.

   An alternative might be one of the insulated roof systems where EPS of various thicknesses is bonded to corro sheet, though I don't know the complexities.

   Posted Tuesday 1 Dec 2015 @ 8:30:47 pm from IP #
6. 

   axess
   Member

   wlb,

   Do you plan to stay in the house long term? It it suitable for "Ageing in place" for example?

   Is the existing roof in good nick? IE: no rust, damage etc?

   You said the Zincalume is nailed to the roof battens not screwed. So there might be damage to the sheets upon removal?

   What about the gutters/downpipes- are they due for replacement?

   I would be tempted to get a couple of quotes to remove the sheets and re-insulate with at least a high quality roofing blanket if not foam sheets of some sort to fit neatly between the battens as well and taped to seal the gaps.

   Given the 7 degree pitch, replacement of the entire 70 mm thickness with a composite insulated sandwich type panel might also be something to consider. You could recycle the existing tin for fencing etc or whack it on Ebay maybe to offset some of the cost.

   Beware of condensation issues whichever method you decide on, and remember roof/ladder falls are one of the most common reasons for emergency department visits.

   Contractors are used to having to maintain the integrity of the roof whilst working onsite. They have their own tarps etc. And you might be surprised how quickly they can do the job.

   Posted Tuesday 1 Dec 2015 @ 8:53:39 pm from IP #
7. 

   RuffTuff
   Member

   "and remember roof/ladder falls are one of the most common reasons for emergency department visits."

   No they're not!

   Posted Tuesday 1 Dec 2015 @ 10:48:44 pm from IP #
8. 

   Morbo
   Member

   I put it this way:
   -colorbond roof lightest grey there is
   -underneath 50mm anticon (thats some bulk insulation with foil)
   -under the rafters I left the sarking from when the roof was black concrete.
   Result: roof inside is same as ambient, trailing behind by 1/2 to 1 hr. Even in full sun.
   I suppose thats as good as it gets unless there would be thermal mass inside the roof.

   Posted Tuesday 1 Dec 2015 @ 11:12:48 pm from IP #
9. 

   wlb
   Member

   Lots of good responses. Thanks. Some I had already considered but they have triggered some new thought in that area, and some I hadn't.

   I was planning to do it myself, with assistance, hence the need to have a temporary weatherproofing arrangement prepared.

   We're in West Gippsland so the extremes are not too bad, although it is getting hotter of course.
   Adding another roof above and leaving the existing sheeting in place is an idea worth considering.

   70mm is certainly not much when there is no air gap or sarking.
   I had considered adding insulation against the underside of the ceiling but decided against it. Adding sufficient would lower the ceiling too much. If the roof was higher I would seriously consider filling the cavity between the deep beams with insulation and adding a new plasterboard ceiling below the beams. But that would reduce the ceiling height at the walls below 2.4m. The ceiling height at the walls is not quite 2.5m and it rises to the central main beam, but even adding 50mm under the ceiling would reduce the ceiling height more than I would like visually. I'm not a fan of low ceilings and the existing height is borderline to my eye. I'm also not a huge fan of exposed beams when the ceiling isn't high, but I find them acceptable if they are substantial. Adding any useful insulation between the beams will visually reduce their depth and that will have a negative visual impact in my opinion. However I do intend to add a sheet of plasterboard to the surface of the lining boards so we can have a smooth white ceiling.

   I'll have a search for those new systems with insulation bonded to corrugated roof sheets.

   I hope we're there for another 20 years - deteriorating in place.
   The roof sheets must be 25 to 30 years old now (we've been there 17) and some require replacement due to corrosion below things like the wood heater flue and TV mast. I had assumed that I would be replacing all sheets when the time came as I want to eliminate 2 old skylights and other roof penetrations.
   The old spring-head nails are now loose due to timber shrinkage and movement and should come out without too much effort or damage.
   New spouting will be needed and all flashing and the ridge capping would be replaced anyway.

   I'll be sticking with uncoated Zincalume, not Colorbond. Apart from its better reflection I'd still rather drink water off an old zinc and aluminium roof than an old Colorbond roof, despite the fact that Colorbond has now been around for a very long time.

   We are planning an extension and after that there will be no penetrations through the existing building's roof, and no TV mast. The PV array currently on the roof will be relocated to another building.
   After reading all your suggestions I'm beginning to think that the way to go is to remove the current sheets a few at a time, fix the insulation by adding more and filling the gaps, then refitting the existing sheets. Then, after the extension is finished, add battens, more insulation and new roof sheets above.

   Posted Wednesday 2 Dec 2015 @ 12:18:18 am from IP #
10. 

    wlb
    Member

    One thing I did forget to mention that needs to be done with at least parts of the existing roof sheeting removed, is to install 240V wiring for ceiling lights. So fixing the insulation problem is not the only reason for taking sheets off the roof.

    The house only has 240VAC wiring from floor level up to bench height, for power points. All lighting is by 24VDC and all light fittings are wall mounted. The only ceiling mounted 240VAC lighting is in the kitchen and lounge areas where I was able to get access by removing flashing.

    Posted Wednesday 2 Dec 2015 @ 3:02:43 am from IP #
11. 

    axess
    Member

    You are quite correct RuffTuff.

    I assume most admissions are for other acute episodes, heart disease and chronic conditions such as diabetes etc.

    However falls from ladders tend to affect men over 50 who are working in the domestic area more than many other injuries. There is an interesting report about their high level of presentations to emergency departments if you google:

    Ladders Revisited_Medical Journal of Australia.htm

    The level of ladder related workplace injuries has fallen (no pun intended)since the introduction of more stringent WorkCover requirements and training. Not so in the domestic sphere.

    This is the point I was trying to make very badly.

    Posted Wednesday 2 Dec 2015 @ 5:35:55 am from IP #
12. 

    Johnnojack
    Member

    wlb, Did you notice any evidence of condensation within the 70mm ceiling space? According to those who now won't even do such construction without a vapour barrier under the tin your ceiling should be ruined. I'd be happy for you to prove them wrong. The roofing bonded to corrugated is very expensive.
    http://www.bondor.com.au/products/roofing/insulroof
    Using it will push the height of the roof up anyway unless you used thinner roof purlins. So you may as well save your money by buying plain zincalume and double up the purlins to get more space for insulation anyway. I second Johnmaths suggestions. RFL plus bulk insulation to achieve something approaching R5. That would be the minimum recommended for your area anyway I would have thought. With just 70mm you can only fit R1.5 of fiberglass batts or you would have to find some new miracle insulation. Bite the bullet as they say, and raise the roof.

    Posted Wednesday 2 Dec 2015 @ 11:11:36 am from IP #
13. 

    wlb
    Member

    Yes, I'm always careful on ladders and roofs.

    No I've never seen any evidence of condensation. But that's not to say it doesn't occur. It's just not evident from the underside of the ceiling. However, there may be sarking under the roof sheets. I don't know. The flashing I removed to run the wires through for the ceiling lights in the kitchen and lounge didn't allow me to see above the bats. I guess I'll find out when I lift the first sheet.

    I now need to figure out the best way to add new battens above the existing sheets.

    I think my plan will now be to lift the sheets a few at a time, run the necessary wires for lights, fill the gaps in the old insulation or replace it (depending on what I find), remove the 2 skylights and insulate and cover the holes, and then after the extension is finished, add a new insulated roof on top, choosing the insulation according to the standard of what is below. This will give me a better roof sooner and the whole project will be broken into 2 smaller ones.

    Posted Thursday 3 Dec 2015 @ 1:55:52 pm from IP #

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