1. Compact Form or Surface Area to Volume Ratio or Form Factor
Sketch of the house's thermal envelope
The compactness of the building has such a big impact. Being connected to neighboring buildings also reduces the surface area. The effects of these are exponential. This house is two-storey so almost cube-like form with one wall attached to the neighbouring unit, eliminating an exterior face. In PHPP, Form Factor, the external surface area to the treated floor area is used as a measure of compactness.
We previously looked at Enerphit for a detached single-storey house stretched out house. We couldn’t get the EnerPHit modeling method to work and had to use the more expensive component method. This project works so well in the modelling method that it can reach, on the first pass, EnerPHit with double glazing and possibly full Passive House Standard with triple glazing. To get the same results less insulation is needed. The specification and cost of the windows can be reduced.
The compactness of form should be one of our guiding principles in building design if we are serious about sustainability. Can we justify long stretched out detached single-loaded houses when medium or high density will always be massively more efficient in energy use (and embodied carbon)?
A semi-detached house may be less appealing in the real estate market but with my Passive House training, I saw it as a bonus.
2. Raised Timber Floor
An existing concrete slab is unlikely to be insulated. Even one build last year! At best you can only retrofit edge insulation. You can get a dispensation for the concrete slab when seeking EnerPHit certification but it's still a loss of real-world performance. State Houses were among the first houses to have floors raised well off the ground, compared to villas and bungalows. Plenty of access for a damp-proof membrane and a significant thickness of well-encapsulated insulation.
3. Restrained Well Designed Window Area
Original Elevations - there will be a couple of sliding doors now
These 1940’s state houses have carefully considered window placements. They are efficient in their use of windows while still providing excellent daylight. The bedrooms have a 1200mm sill height, which is great for privacy. There is a new townhouse down the road with full-height glazing in second-floor bedrooms!
We are fed a diet of floor-to-ceiling architectural images but indiscriminate glazing at low level doesn’t contribute to daylighting while increasing heat loss. Better to frame the view.
4. Steep Roof Pitch
The first draft of eaves detail - it got better
I had not expected this, but the 38-degree roof pitch greatly reduced the thermal break effect at the eaves compared to what a low-pitch roof could have provided.
5. Timber Framing
A new novelty in some places overseas, timber by far has the lowest thermal conductivity of all common building materials. And it stores carbon. There is no need for tricky internal insulation. No need for expensive re-cladding.