Alternative Technology Assn Forums

1. 

   tasvalleydweller
   Member

   I live in a narrow valley in southern Tas - cold winters with reduced sunlight. We have a split level house with cathedral ceilings - exposed beam style. The gap in our roof is only a rafter thick.
   Each winter we have condensation issues (initally water dripping through - we have pine cladding ceiling). We were told to get insulation and replace sisalation paper and did so (R3.5 batts). As you can tell, I did no research at all so now our tiny gap is filled with squished insulation with sisalation on top and roof iron on top of that - NO AIR GAP!!!

   SO, what do I do?
   1. remove insulation and go for thinner with same or better R rating, add some vents and hope for the best...
   2. raise the roof to create an air gap, add some vents and hope for the best...

   Does anyone have any advice or experience with this problem as I have not met any tradesmen who know enough to provide definitive advice.

   Thanks,
   TasValleyDweller

   Posted Thursday 28 Jul 2011 @ 10:15:06 am from IP #
2. 

   dymonite69
   Member

   You seem to have a interesting scenario. I am not sure how squished R 3.5 would behave in comparison to non squished R 1.0. I am sure the manufacturer wouldn't have tested it this way despite your installer's creativity. Have you measured the surface temp of the underside of the ceiling? My gut feeling is that you should leave it there and look other reasons why so much moisture is getting into the house. What are you typical indoor humidity levels?

   I can't see a better insulation solution without creating a false ceiling.

   Posted Thursday 28 Jul 2011 @ 11:58:15 am from IP #
3. 

   connecting
   Member

   I am curious
   When you or the trades person installed the sisalation paper did they cover the whole roof area including the ridge?
   And also can you tell me what type of sisalation paper used?
   I am thinking three things here.
   Use of a gas heater.
   Compressed sisalation.
   Wrong sarking used or installed incorrectly
   There are a few different types of sarking, some breath others stop condensation from coming through from the roofing iron its self, like a water barrier which is what you should have.
   But in some cases where the ridge is closed up as in the paper is wrapped right over the ridge (very top of roof), the heating inside to cooling at the ridge ceiling will cause condensation at the peak and start running down on the underside of the sarking causing the bats to get wet and soggy.
   Another thing with cathedral ceilings is that you must not compress the batts to the top of your timber ceiling; there should be an air space between.
   I presume you used the old type glass wool insulation and not polyester batts.
   If you are using a gas heater specially the older type I would suggest you replace it as soon as you can or specially have a gas plumber check it out, they do cause a lot of condensation and other dangerous gases.
   Please reply I am interested in what you have,

   Posted Thursday 28 Jul 2011 @ 11:06:19 pm from IP #
4. 

   GBD
   Member

   I suggest you have a read of this publication that was released on the 20th July 2011.

   http://www.abcb.gov.au/index.cfm?objectid=49833C4B-B29A-11E0-8548001143D4D594

   Australian Building Codes Board - Condensation in Buildings

   There are quite a few issues raised that many may not be aware of.

   Also contains case studies of retrofitted insulation that has caused problems in a skillion roof, high roof ceilings, along with a new build in Victoria in the fire area as a new home to replace a lost one.

   It's a good publication and one that anyone planning on doing a retro fit of insulation should consider as a MUST READ to be aware of issues you could potentially create while you are trying to do good.

   Includes notes on walls, floors and ceilings and condensation issues that can be caused by not insulating the area correctly, using the wrong type of vapour barriers and issues caused by putting them wrong side of the wall / roof / ceiling.

   Posted Sunday 31 Jul 2011 @ 1:06:50 am from IP #
5. 

   Oldfellow
   Member

   If the sarking is performing correctly, ie keeping out rainwater, the problem must be due to condensation. This will occur when relatively moist warm air comes into contact with the cold surface of the sarking. Thw warm air is cooled and when the temperature drops below the dew point the air's capacity to hold moisture as vapour is reduced and the falling temperature squeezes out the excess moisture as condensation.
   The moist warm air must originate within the house and an impermeable vapour barrier installed above the ceiling (below the insulation) will prevent the moist air from getting into the insulation. Providing the insulation is able to maintain the temperature of the ceiling above the dew point of the air condensation will not occur.
   This could be effected by removing the boarded ceilng and installing a vapour barrier, being careful to ensure continuity by taping joints, etc.The ceiling boards could then be put back or replaced with something else.

   I also endorse the advice regarding junking your gas heater.

   Hope this helps.
   Oldfellow

   Posted Sunday 31 Jul 2011 @ 4:27:27 am from IP #
6. 

   tasvalleydweller
   Member

   Thanks for all your advice and questions.

   Firstly, the sarking is new and does not allow moisture through. Issues seem only to arise during winter on nights when we have frosts - very cold nights.

   We don't have a gass heater we have a wood heater.

   I'm interested in the comment about the insulation against the timber ceiling. How do you prevent it from not being laid directly on the ceiling?

   I have mapped my house for signs of water damage on the timber ceiling. My split level roof acts as 2 roof spaces as they are not connected. The most damage by far is in the top roof which is effectively south west facing. The main rooms affected are those that receive the least amount of winter sun. The damage can be roughly generalised along 3 main lines of the roof running longways, not from the ridge to the gutter, as if condensation is running from the ridge, hitting a barrier of some type causing it to drip down on to the insulation, soaking it and damaging the roof. Could this be the case?

   Not sure how the measure humidity levels, is there a device readily available?

   Tasvalleydweller

   Posted Saturday 13 Aug 2011 @ 11:56:16 pm from IP #

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