Alternative Technology Assn Forums

1. 

   supa007
   Member

   Hi all,

   Just wondering if anyone can chime in on our new build. We are going to build on a block within meters from the beach in SE QLD. Our Brisbane based architect doesn't think we need a well insulated house in our sub-tropical climate, with priority given to cross ventilation.

   But my question is why can't I have both? Can't a well sealed, well insulated house be also well ventilated? The dilemma is obviously we want to maximize window / door openings to take advantage of views and the outdoors, but that sort of defeats the purpose of a well insulated construction.

   So, my question is does it make sense to spend extra on constructing a well insulated house when all that advantage is lost through windows and doors?

   Kevin

   PS. Block is 50m (north/south) x 20m (east - beach/west - inland)

   Posted Saturday 22 Jul 2017 @ 12:49:21 am from IP #
2. 

   Bushwalker
   Member

   Current overnight temps in Robina are 7-10C. If you are in an elevated zone heading up to Mt Tamborine the temps will be even lower.

   So you could have windows open during the day with 20+ degrees in winter, and close the ventilation as the sun comes down. Insulation would protect the home from the low overnight temps IMHO.

   Much easier to insulate during build.

   Posted Saturday 22 Jul 2017 @ 7:04:58 am from IP #
3. 

   Catopsilia
   Member

   Hi supa007

   I hope you may find this post on "Adaptive Comfort" in the "Low Energy Houses" thread helpful.
   http://www.ata.org.au/forums/topic/3/page/10?replies=295#post-99399

   According to data for Southport, the following apply:
   July mean max: 20.6
   July mean min: 9.2
   July mean temp: 14.9
   July record daily min: -3.9

   January mean max: 28.6
   January mean min: 20.4
   January mean temp: 24.5
   January record daily max: 39.0

   Applying the Adaptive Comfort Standard gives:
   July 80% satisfied lower comfort limit: 19 degrees
   January 80% satisfied upper comfort limit: 28 degrees

   In the case of a house (or tent) with hardly any insulation, one can ask:
   Will it get too cold in July?
   Yes it will! With a lower comfort limit of 19 degrees, even an average July (min 9.2 degrees) will get much colder than that. As for the record daily minimum....

   Will it get too hot in January?
   Perhaps. With an upper comfort limit of 28 degrees, an average January (max 28.6 degrees) will be bearable. But half of all January months have max monthly temperatures hotter than average. Then the record daily maximum (39 degrees) was quite nasty.

   I think you may appreciate having some insulation.

   That is all about the air temperature. The house will also be heated by the rays of the sun, and will be cooled by radiation to space at night. That calls for aluminium foil insulation in the roof at least.

   Posted Sunday 23 Jul 2017 @ 5:11:01 am from IP #
4. 

   supa007
   Member

   Thanks for the reply Catopsilia. No doubt there will be insulation for the house. What I'm specifically asking is whether building with structural insulated panels (~R2.9 walls, ~R5.5 roof) might be an overkill, given there will be plenty of openings for windows, bifold doors, etc.

   Of course if the cost is equivalent to traditional construction with standard insulation then it's a no-brainer. I'm just trying to work out independent to the architect whether there might be additional costs involved, if the additional insulation properties still stack up when there are big openings with low/minimal insulation.

   Kevin

   Posted Tuesday 25 Jul 2017 @ 11:55:59 pm from IP #
5. 

   arttt
   Member

   If you look at this link (Brisbane is probably the closest record) you will see that SE QLD has some of the lowest energy needs in Australia to keep a house comfortable.
   http://nathers.gov.au/files/publications/NatHERS%20Star%20bands.pdf
   If you are only metres from the beach then the temp extremes will be somewhat further moderated by the water temp.
   http://www.surf-forecast.com/breaks/The-Spit/seatemp

   In this case I dont think you will see much benefit from spending extra for high levels of insulation. Sure do the standard amount (something like R2 in stud walls) and it doesnt hurt or cost much to put a bit more then standard in the roof space. If the SIPS are cost competitive then no reason not to use them.
   You will appreciate windows that seal well in winter with strong winds close to the coast so pay attention to that and you have already identified cross ventilation as important in summer.

   This is the most important bit.... You should pay attention to excluding summer sun and letting in some winter sun with well though out window orientation and eave sizes. If you get that right the house should be comfortable year round.

   Not wanting to be negative but I hope you have thought about what happens to your block when sea levels rise and storm erosion increases.

   Posted Wednesday 26 Jul 2017 @ 12:57:19 am from IP #

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