lorri
Member
Hi We are looking to build and in the quote from the builder said that it would be a waffle pad, is there any need to add side insulation to a waffle pad? I thought I better check.
House is in southern Tasmania,north facing,we have no set house plan yet,just one we think will be the one so at this stage we can change things to suit.
Cheers Lorri
The heat loss from a typical slab on ground is around 100w/degree temperature difference.
Check out the link belowm if you want to work it out more accurately. http://www.anewhouse.com.au/2012/10/floor-insulation-slab-on-ground/
If the builder won't do the perimeter insulation you can always lay insulation under the paving around the house later for a similar effect.
lorri
Member
Thanks guys, will ask builder again and ask for price, if he won't do it we will do the paver method.
I am making a big list of questions for the builder to get more prices for things, any things I should ask for that don't cost a fortune, have to keep to a budget.
Cheers Lorri
Make sure you get enough power points in the right locations builders standard provision is never enough. Usually costs around $80 for an extra double. See this link for more info http://www.anewhouse.com.au/2012/02/electrical-planning-general/
Also make sure you right size your windows. . . My last builder didn't charge extra for reducing the size of windows(increasing the area of brickwork)
pulpo
Member
Hmm Waffle pods.
Waffle pods were designed to eliminate excavations particularly in reactive soils.
Seems to be standard method of domestic house slabs.
For insulation waffle pods are very average, especially brick veneer, nothing around the edges
If I was building a slab it would be the standard raft and beam with everything insulated except the piers.
Waffle use more concrete.
As for edge insulation, should be required, it is if placing in slab heating.
Is it brick veneer?
I have no end of issues with this requirement.
The above diagram is the slab edge (cannot cut and paste sketch?)
The top part of the slab is where the insulation in my mind should be.
There is a gap between the bricks and this part of the slab.
Any insulation is fine, 30mm Expanded or extruded foam is fine.
Some builders pour in perlite, once the first couple of layers of bricks are up.
You just have to be careful of the drainage.
However the standards mention about insulated of the external part of the slab if inslab heating.
The part of the slab which the bricks are resting on.
In which case it has little benefit in my view.
You could ask the certifier if they have a view.
If placed on the outside it must be extruded polystyrene XPS, it must be protected, flashing or render.
And you must have termite protection for the joint between the foam and the slab.
So termites cannot come up between the outside slab and the XPS foam, you would have no visual inspection.
Brick veneer is not easy to insulate slabs, in theory both parts of the slab should insulated.
Good Luck with the house build; a bit nervous and exciting at the same time.
Pulpo
Nat Vegan Green
Member
Lorri have you checked out the Your Home - Design for Climate section for Tasmania. Good basic info on insulation and glass to thermal mass ratios etc. http://www.yourhome.gov.au/passive-design/design-climate
Johnnojack
Member
Slab edge insulation seems imcompatable with both termite control and builders. In 40+ years of interest in building I have yet to see it done. (I admit it could be hidden from view). Waffle pod more concrete? I don't think so. My sister and her husband saved $20k with a waffle pod footing. They built where concrete is much dearer than in the cities.
pulpo
Member
Yes waffle pods are in theory less concrete but most slabs I see, I question that.
The standard raft and beam slab would use less concrete if the engineer was good at designing a slab.
If you add an extra $15m2 for pods or excavate for raft and beam.
Pulpo
"Yes waffle pods are in theory less concrete but most slabs I see, I question that.
The standard raft and beam slab would use less concrete if the engineer was good at designing a slab.
If you add an extra $15m2 for pods or excavate for raft and beam."
There are valid reasons for using Raft and Beam Slabs or Waffle pods but the engineer being good enough is nothing to do with it.
Waffle pods use less concrete, and have less waste concrete. (because site workers are unable to excavate accurately the beam shapes the builder has to over order concrete rather than risk running short
Johnnojack
Member
Bash you are right, and if the trenches collapse at all it means more and more concrete. Been there done that, don't remind me. 
lorri
Member
Thanks guys, I guess it all comes down to if the builder will do it and if he says a waffle slab is the only choice. We haven't had any soil tests done yet as we won't be building yet for quite a while, I just want to get the most for my money. Yes Nat I have looked at the website,it's great. I need to write a list of must do/ haves. So any ideas would be great.
Cheers
Lorri, I have been advised over and over that waffle pods are a big problem structurally. In our first passive house Superpod building we didn't do it. the engineer said no way. One of the big building companies has been sued repeatedly for failures in waffle pods.
Why are you doing a concrete slab anyway?
If you want a house that stays warm throughout the house without heating in winter/cold days, you must fully insulate under the floor.
If you want a passive house, is via the International Passive House Standard, you can get clear data on how the temperatures of the house will naturally perform without heating.
Bushwalker
Member
Superpod said:
Why are you doing a concrete slab anyway?If you want a house that stays warm throughout the house without heating in winter/cold days, you must fully insulate under the floor.
If you want a passive house, is via the International Passive House Standard, you can get clear data on how the temperatures of the house will naturally perform without heating.
http://www.phinz.org.nz/faq/what-role-thermal-mass-certified-passive-house
For summer though, and in other usage situations with high internal heat gains, e.g. offices and schools, thermal mass may be a game changer for comfort, particularly when the heat absorbed during the day can be ‘discharged’ again over night through increased night-time ventilation. Buildings with appropriate external shading, especially of East and West facing windows, should however not need extra thermal mass to stay comfortable year-round.
Although thermal mass can be beneficial in certain situations, the first priorities for the design of a building should always be a high performance thermal envelope with excellent airtightness and effective shading.
If you have thermal mass, make sure it is isolated from the outside and pay attention to thermal bridges. Insulate under that slab. 
Yes good stuff!
Depends on your climate and reason for thermal mass.
If you think thermal mass is needed for heating in cold weather, it isn't, if you build to the passive house standard.
If you want a concrete slab to help feel cooler in summer it can be great for that. (In fact I love a concrete floor to help you feel cooler in summer).
Thermal bridges through the floor may not be a problem in a hot climate - the Passive House Standard may allow you not to insulate the floor in a hot climate.
All depends on climate and overall design.
