dymonite69
Member
Remember radiant heat is efficient but convective cooling isn't. To prevent overheating it is essential to keep the sun off the mass during the day and then maximise cross ventilation at night. It becomes even more problematic if night time temps don't fall dramatically.
A house with excessive mass may respond too slowly to changing conditions.
johnpao
Member
GBD:
The system is off grid - but I thought extra panels could cover the air con use, given that when it would be on there would be enough sun as well. Is your system 6.5kw of panels or is that the average input of power?
hasdrubal:
Have looked into straw bales but they do take up a lot of space with their depth - we have a fairly limited footprint of about 6.5 m x 13m for the slab area. But their R values are impressive!
Russell:
Not leaving those babies just yet...! This is a house I'm building with 3 others (my sister-in-laws...) - I hope to spend a year in Mudgee 3-4 days a week, and then maybe rent it out - would need to be someone green minded to live within the parameters of the house though - could be a market for people who want to drop out for a year or so but without doing the complete sell-up of their house etc (ie midlife tree change without the commitment) The land feels very isolated but in fact is only 26km from Mudgee (on the Sydney side).
The issue of the mass overheating is now the main concern - just checked the BOM site - in summer last year Mudgee had a hot spell:
10 Tu 8.5 - 31.0
11 We 9.1 - 34.3
12 Th 10.4 - 35.6
13 Fr 15.8 - 26.8
14 Sa 10.0 - 33.1
15 Su 11.7 - 36.3
16 Mo 14.3 - 37.6
17 Tu 17.2 - 35.4
18 We 14.2 - 34.2
19 Th 13.3 - 39.4
20 Fr 17.5 - 41.1
21 Sa 19.8 - 41.0
22 Su 20.1 - 38.3
On the high 30 temps there were wind gusts of up to 70 kph...
Some nice low overnight temps - but would the mass cool down enough?
dymonite69
Member
This is our experience during summer. We have slab only mass with about 40% uncovered. Very little sun gets on the floor due to good orientation and shading. We can manage about an 8-10 degree gradient over the day e.g. 36 outside 28 inside (free-running, no air con).
It will cool to around 18 degrees at night. By midnight it will still be around 20 degrees. It probably would take the rest of the night to equilibrate.
Slab mass probably cools quicker due to ground coupling and lower ground temperatures. I would expect that wall mass won't lose heat as fast.
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