A second high-mass solar-passive house was built in 2009 in Strafford Street Manilla, within 300 metres of my house in Monash Street.
My friend Geoff designed his house and used the same builder that I did. Sadly, after five comfortable years in his house, Geoff has passed away. Thanks to his daughter, I can show you the features of the house.
Thermometers, and power bills show that its performance is similar to mine. That is to say, it is very successful!
In Manilla’s climate of daily and seasonal temperature extremes, Geoff rarely needed to use his low-powered reverse-cycle air conditioner.
Length, East-West: 18.28 m
Width, North-South: 9.45 m
Ceiling height: 2.70 m
Room area, Living/Kit/Bed 1/Study: 115.9 m^2
Room area, Bed 2: 13.8 m^2
Room area, Bed 3: 14.1 m^2
Room area, Bathroom: 8.6 m^2
Room area, Laundry/Darkroom: 7.7 m^2
Area of walls: 12.7 m^2
Total House Area (without patio): 172.8 m^2
North wall: double brick
East, west, and south walls: 90 mm stud, including 9.61 m reverse brick veneer
Cladding of stud walls: custom orb (horizontal)
Cladding of gable ends: plain roofing panels with 50 mm foam
Single brick: 17.16 m
Stud wall: 11.66 m
Windows (and two glass doors)
All double-glazed 3/6/3 in uPVC frames
(North-facing window area is 16% of the floor area of the house.)
North-facing: 27.00 m^2 (76%)
East-facing: 3.84 m^2 (11%)
South-facing: 4.50 m^2 (13%)
West-facing: 0.00 m^2 (0%)
Total: 35.34 m^2 (100%)
Walls (double brick, reverse brick veneer, and stud walls): R = 2.0
Ceiling: R = 2.5
Roof and gables: R = 2.5 (foil)
Floor slab: None
Roof pitch, south: 20 deg
Roof pitch, north: 12 deg
Northern eave width: 1.275 m
Roofing: custom orb steel in pale colour
Vents in gable ends with adjustable louvres
Electric exhaust fans above
area 172.8 m^2;
thickness: 100 mm;
volume: 17.28 m^3;
mass (@2.1): 36.3 tonnes
Enclosed brick walls: (Includes the reverse brick veneer, interior brick walls, and inner leaf of double brick walls.)
length 35.73 m;
height 2.70 m;
width 0.11 m;
volume 6.63 m^3;
mass (@1.7): 11.3 tonnes
Total thermal mass of bricks and slab: 47.6 tonnes
The design of Geoff’s house and my house
Since Geoff’s house in Strafford Street and my house in Monash Street are both successful solar-passive designs suited to this climate, it is interesting to compare the way they were designed and built. I use section headings from the web-site “YourHome”.
Design for climate
In the climate classification of the Building Code of Australia, Manilla, NSW is in Zone 4: “Hot dry summer, cool winter”, along with Tamworth, Mildura and Kalgoorlie.
While I designed by imitation of other houses, such as the Wombey house in Canberra, Geoff, an engineer, bought a copy of Steve Szokolay’s program “Archipak” (See Note below.) and analysed every aspect of his project, such as sun tracks, glazing, insulation, and thermal mass.
Within the constraints of the blocks, we each faced the house near true north, Geoff’s being offset ten degrees east, mine eight degrees west. Both houses run east-west, and have most windows (76%, 70%) facing north, and no windows facing west.
We specified eaves to shade out the sun for about seven months, with a slope of 2:1 from the edge of the eave to the foot of the window.
My block has space to the east and west for various kinds of shading, including mature trees; Geoff’s block does not.
Passive solar heating
In Geoff’s house, winter sun shines only on the tiled slab; in my house it also shines on internal brick walls.
At Manilla, summer humidity, which ranges from 30% in the afternoons to 80% at sunrise, is not so high as to cause discomfort. On the other hand, cooling breezes are rare.
Both houses use summer night-purging with a stack effect for cooling. I use ordinary desk-type fans, Geoff has three large ceiling fans and two roof fans.
We had a conscientious builder who took sealing seriously.
We used about the same amount of insulation in the roof, ceiling, and walls (It is hard to be sure.) I used perimeter insulation around the footings; Geoff did not.
We fitted heavy, lined curtains with pelmets to the windows. Geoff’s were home-sewn and hand-drawn; mine were motorised.
This climate of temperature extremes demands thermal mass!
I find (on re-calculating) that our thermal mass installation is similar: for internal brick walls Geoff has 11.3 tonnes, and I have 16.8 tonnes; for the slab, Geoff has 36.3 tonnes and I have 28.3 tonnes. So the total is (for Geoff) 47.6 tonnes, (for me) 45.1 tonnes.
I am convinced that the perimeter insulation around my footings adds more than 150 tonnes of effective mass to my house, and I would expect Geoff’s house to lose some of that benefit.
We both used plain double-glazing.
We restricted the window area to prevent excessive heat losses and gains. Geoff’s house has 27.0 m^2 of window facing north, which is 76% of the total window area and 16% of the total floor area. My house has 19.7 m^2 of window facing north, which is 70% of the total window area and 13% of the total floor area.
Our house styles
While both these houses are modest in size and in appearance, and neither wastes energy, there are differences. Geoff took “open planning” to an extreme: most of his house is one large room. I avoided “open planning”: most of my rooms can be closed off.
Geoff has sensibly stuck to a simple rectangular shape that is cheap to build (they say), minimises heat losses, and avoids one part of the house shading another. I was seduced by the views I could get from a ridge-top, where the house could not be built so simply.
An outline of the program “ARCHIPAK” is on Page 132 (“Method Sheet M 1.9”) of the Third Edition of “Introduction to Architectural Science: The Basis of Sustainable Design” by Steven V. Szokolay, Third Edition, Routledge, 2014.
The Wombey House (my inspiration) is No. 20 in the book “Australian Solar Houses” by Matthew Parnell and Gareth Cole, Leura, NSW, Second Back Row Press, 1983.