Buildings can incorporate sun control that admits warming sun in winter and blocks hot sun in summer. It works best on a north-facing aspect. This diagram is for the northern hemisphere but the principle is the same (source: Architectural Record)

One of the issues raised by the Victorian Government’s discussion paper, Better Apartments, is the “lack of controlled sunlight access to apartments”. Access to direct sun is different from access to natural light and these are treated separately in the Government’s paper (I discussed natural light last week; see Should natural light in apartments be more tightly regulated?).

Direct sunlight is important, the paper tells us, because it “promotes health and psychological wellbeing”. It can also directly affect the heating and cooling load on an apartment.

Providing for thermal comfort through the design of the building, rather than relying on mechanical services, can make the operation of buildings more resource efficient, reducing peak demand on energy infrastructure and improving resilience to climate change.

The paper notes that access to sunlight is primarily determined by an apartment’s orientation. It poses a very big question: “Should there be rules to ensure a majority of apartments receive sunlight?

The first thing to note is the “health and wellbeing” rationale for regulation is hyperbole. As I discussed last time in relation to daylight, while some minimum exposure to sunlight is doubtless generally desirable for human health, that’s not what’s at issue here.

The question on the table is whether or not significant numbers of apartment residents are likely to suffer ill health as a direct and sole consequence of living in dwellings that have little or no exposure to sunlight. A related question is whether or not regulating some minimum level would actually address any such deficiency in the residents’ state of health and wellbeing.

These are more specific – and more demanding – issues than simply stating baldly that sunlight “promotes health and psychological wellbeing”. Other factors need to be taken into account e.g. all the other ways residents are exposed to sunlight, such as on their way to work or school.

Another thing to note is that the apartments being built in Australian cities are already relatively thermally efficient compared to other dwelling types, especially the detached houses being built in the fringe growth centres.

That’s due to a combination of factors, including their small size (many are “dogboxes” according to Victoria’s Planning Minister!) and the fact that most are well-insulated by neighbouring units above, below and on up to three sides.

I’m also bemused by the idea that only “a majority of apartments” need to get direct sun. If the benefit of sunlight is so important that it warrants mandating some minimum exposure, it should apply to all apartments.

I’d like to know what it is about the other 49% that means they don’t need mandated sunlight. Anyway, does the Government even know what proportion of existing apartments receive sunlight? Could it be that a majority already get an acceptable level?

If it’s serious about having a meaningful debate on this issue, that’s the sort of information the Government should have provided in its discussion paper.

But when it comes to the big question posed by the discussion paper, I’m doubtful about the wisdom of bringing in rules mandating how much sunlight must fall on an apartment. The leaked draft of an earlier version of the discussion paper reportedly proposed that 90% of apartments must receive direct sunlight and all living areas must face north.

Residents who appreciate direct sun on their windows or balcony will seek out an apartment that offers this amenity (due north is best in the southern hemisphere) and pay a premium. But others will trade-off less sunlight for other attributes, perhaps a better street.

While it would depend on how much sunlight is defined as the minimum, these sorts of proposals have the potential to reduce the number of sites that could support a viable development. Moreover, they could reduce the yield from any given site.

It’s likely fewer projects would proceed, leading to a consequent deterioration in affordability; the biggest impact would be felt by buyers at the lower end of the market. Perversely, such a policy might encourage ever-higher towers so that more apartments could be in “clear air”.

So while I accept the proposition that orientation is the most important determinant of an apartment’s access to sunlight, I think the cost of regulating some minimum is way too high and the benefits are at best unclear.

I think there’s a stronger argument, though, for intervention aimed at improving the thermal efficiency and comfort of those apartments that actually do receive some direct sunlight. Western sun in particular can impose a large heat load on unprotected windows in summer, especially in the afternoon.

Owner-occupiers might elect to install air conditioning but that solution isn’t always available to tenants (who make up the majority of apartment residents). Even when it is, it adds to running costs and, as the paper notes, increases (largely coal-fired and peak) energy demand.

The debate the Government has started could usefully consider the benefits and costs of requiring mandatory sun control on new apartment buildings.