M+A Architects


How to get Sustainable Affordable Housing on a Budget

  • AUGUST 25, 2015
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When selecting a site for affordable housing, there have been many trends popping up over the last several years. There’s flat sites that are optimal for “aging in place” and larger sites to accommodate renewable energy, but many of these trends may not fit into the ever-challenging affordable housing budget. However, passive heating and cooling design sensibility and technology has been on the rise and when done thoughtfully, can require no cost increases and provide you with sustainable affordable housing.

As defined by EcoMii, passive heating and cooling, or passive design, refers to using “natural elements, often sunlight, to heat, cool, or light a building.” By using a little bit of design layout know-how (and of course, the sun and wind), you can make a huge impact and find yourself with big returns when it comes to energy consumption.

When it comes to selecting a site that can exploit the sun as an energy source, you need to consider: orientation, product type, and layout.

[caption id="attachment_5459" align="alignright" width="284"]Passive Design Image from http://www.ecowho.com/[/caption]

1. Orientation
Choosing the right orientation is one of the easiest things you can do. In locations that are primarily cooling environments, select a site with a large north-south axis. This allows the design team to utilize prevailing cross breezes to ventilate and cool the home, rather than relying on air conditioning or other mechanical means. Conversely, in primarily heating environments, a site with a large east-west axis is of greater importance. This allows the building to maximize the sun’s benefit through south-facing glazing during the colder, winter months. However during the summer months, you should always have a way to shield the south-facing glazing. Passive benefits achieved during the winter will quickly be diminished by the excessive use of cooling if unshaded windows aren’t protected from the harsh summer sun. This can easily be done with the use of large overhangs or sun-shades that permit the lower angle of the sun in the winter but block the higher angle of the sun during the summer.

2. Selection of Product Type
While primarily influenced by market studies, different product types lend themselves more easily to passive heating and cooling than others. Single-family homes are very easily adapted to passive heating and cooling because they have flexibility in their configuration depending on the site available. They also typically feature front porches and overhangs that have the ability to protect glazing during summer months. Also, townhomes with their linear configuration can largely be utilized on sites that are trying to maximize passive heating and cooling principles. Having a long axis, townhomes can be situated with either the front wall pointed south for maximum heat gain in colder climates or they can be oriented to maximize use of prevailing winds for maximum cooling gains.

Elevatored buildings, with an interior corridor, can be one of the more challenging product types with respect to passive design. Because most of these buildings use double-loaded corridors with units facing both sides of the building, not every unit gets the opportunity to maximize the benefits that can be seen through passive design. However, if the project budget can support an elevatored building with units on one side, mass walls and ventilation stacks at the corridor can be used which are two of the most beneficial passive design strategies.

3. Layout of Spaces
The final piece of the passive design puzzle comes through unit layout. Going back to Orientation, we know that the sun path should be focused along the south face of the building in both summer and winter (albeit different angles). If you combine that notion with the sun rising in the east and setting in the west, you have your recipe for how to efficiently layout your units.

The living room, dining room, and family room should be situated in the southern most areas. These spaces get daylight throughout most of the day and capitalize on the most amount of solar heat gain. However, south glazing should be protected during summer months.

The eastern areas are best for the kitchen/breakfast area and bedrooms—provided you’re your residents are early risers. Throughout the year, the eastern areas get an initial solar heat gain first thing in the morning as the sun rises, then later in the day, when a majority of the cooking functions occur, the kitchen will be cooler.

The western areas of the unit can be good for living and dining spaces, but fall victim to the harshest sun of the day. This is due to a very low angle that often creates overheating and excessive glare. I encourage you to provide very little glazing on the west side of the home unless you are in a climate that needs the prevailing winds for cooling. If you have that need, make sure glazing control devices (such as window blinds) are installed.

Since the north facing spaces of the building get almost no benefit to solar heating or daylighting, these are the spaces best suited for the non-habitable spaces like bathrooms, laundry rooms, garages, and stairs.

Passive Cooling Passive cooling diagram from Indian Village Lodge

Passive Design - Built for Affordable Housing
Affordable housing developers, owners and designers are constantly looking for ways to increase the quality of life for residents of housing communities. By infusing the forces of nature into the building, passive design allows the occupants to feel engaged as they reap benefits from the natural elements.

Also, passive design has little or no cost impact. By following the basic principles outlined above, developers and designers can include some level of passive design into almost every type of housing by making the right decisions upfront. Passive design has been used for hundreds of years and will continue to be one of the few design ideas that will stand the test of time.

Here's some other design resources if you're interested in reading more about passive design:

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