8/9/2019 Sanctuary magazine issue 12 - Ask Our Experts - green home feature article

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Ask OurExperts

Our house heats up quickly in summer and we are wondering if we can

add thermal mass to the inside of our house to stabilise the temperature?

 We wanted to get hardwood flooring but should we tile instead? I’m

 worried tiles will be cold underfoot in bedrooms in winter, and I hate

cleaning grout! What should we use on the walls, especially if we decide

to use timber on the floor? Tiles? Stacked stone? Is there a special type of 

thermal plasterboard? — Christie 

 Dick — You could add thermal mass (TM) to either the floor or the

 walls, or both. Be aware that replacing the floor will probably be very 

disruptive. You can add TM to strategic walls by installing rammed earth

infill between studs. The foundations of the selected walls need to be

checked – the key is to have a continuous foundation wall or a strong

 bearer. Soil from your own site is best; sandy loam or sand will need 5

per cent cement. This is tamped solid between sliding strong forms in

150mm layers. This can be exposed as a feature (funky) or covered with

meshed render (smooth). You can also use conventional TM l ike bricks.

The structural issues are the same, but you might replace the whole wall

rather than adding to the existing frame. [Ed note: There is an interesting

discussion regarding Phase Change Plasterboard on the ATA forum:

 www.ata.org.au/forums. Search for “Phase Change Materials”.]

My partner and I are building a house which will have extensive timber

decking. We are concerned about termite attack. We are both reluctant

to spray poisons. We understand that if we incorporate blue metal as a

 base to the decking that this may provide a barrier. Can you confirm or

otherwise provide us with s ome eco-friendly alternatives. — Jane 

 Dick — Blue metal is not a barrier to termites. Crushed granite, as found

in Granitgard, is. It must be installed in particular ways by an accredited

installer and will give excellent non-toxic performance, if you keep the

maintenance up to the post bases. You could also use a resistant speciesor treated timber post in-ground, but you need to satisfy yourself of the

exposure risk to treated timber. Class 1 durability timber for in-ground

use avoids the treatment issue, but sustainable suppliers are hard to

find. Try The Woodage in NSW. Class 1 for above-ground use with

galvanised steel post bases is yet another option. But then you need to

consider whether you need the in-ground cantilever effect to contribute

to bracing, or if you can provide that above ground... All good fun to work

out!

I have built a north-facing house with substantial standard glass to the

north including clerestory windows which allow the winter sun onto our

concrete floor. The only catch is that we are actually finding the sun so

glary that if it wasn’t for our beautiful view it would be tempting to put

our blinds partially down, even in winter. Is there a way to retrofit tinting

or similar onto the clerestory windows to reduce this glare and summer

heat and ideally reduce heat loss in winter as well? —  Jenni 

 Lance — You can retrofit tinting to any window. Providing there is

nothing rubbing on the glass and the window is accessible right to each

edge, there should be no problems. There are many new-style selective

films available – one of the best is V-Kool ( www.v-kool.com.au).

Can you give me some advice on the difference between evacuated tube

and flat panels in the generation of hot water? Which ones are the most

efficient and cost effective? — Grahame 

 Lance — They are actually fairly similar in price and efficiency. The

evacuated tube collectors are considered to be a bit more efficient in

colder, cloudy weather, but there are very few evac tube systems available

in close coupled format (ie, with the tank mounted on the roof above the

panels): they are virtually all split systems. These have the panels on the

roof and the tank on the ground, and use a pump and pump controller to

circulate the water. Due to the added complexity, these are more prone

to failure than a close coupled system, which has no pump and works

on thermosyphoning alone. My personal preference is a close coupled

system, so I would install a flat plate system with either a stainless steel

tank or an all-copper tank (which usually work at a reduced pressure).

For boosting, the best option is a high efficiency instantaneous gas unit

such as a Rinnai S series solar booster or a Bosch 26eco+.

Your design, product and specification questions answered by our expert 

columnists Dick Clarke and Lance Turner.

Dick is principal of Envirotecture, a sustainable building design firm

in Sydney. Lance is the ATA’s technical editor and a columnist in

Sanctuary’s sister magazine, ReNew.

Email Ask the Experts at sanctuary@ata.org.au