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ASHRAE funding research on building shape and density

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by Jessica Krippendorf

The only Canadian to be awarded a Grant-in-Aid grant from the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) is studying the effects of building shape, site layout and orientation on the design of net-zero energy solar neighbourhoods.

The only Canadian to be awarded a Grant-in-Aid grant from the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) is studying the effects of building shape, site layout and orientation on the design of net-zero energy solar neighbourhoods.

Caroline Hachem has master’s degrees in architecture and building engineering, and is a PhD candidate in the Building, Civil, and Environmental Engineering department at Concordia University.

Her study investigates the effects of building shapes, density and orientation on solar potential in neighborhoods of different layouts.

Her work is a comparative study of basic housing shape plans — square, rectangle, L, U, H and T shapes — and variations of L and U shapes, as well as housing density and site layout.

Various configurations can result in energy generation of up to 50 percent higher than standard rectangular housing shapes.

“Each shape can offer some benefits and some penalties; tradeoffs should be made between these,” said Hachem. “Some configurations are more suitable to be implemented in some layouts than in others.”

There are some basic principles to follow.

“A building shape first should correspond with its neighbourhood context, and also, probably the most important, satisfy the needs and the comfort of its occupants,” she said.

Site layout designs such as sites with curved roads (for example, cul-de-sacs) and sites with straight roads are also under consideration. For example, in a curved road the L variants can be more advantageous than rectangular houses placed around the curve, said Hachem.

Orientation, particularly in curved layouts, can enable the spread of peak electricity generation by up to six hours.

The shift in the peak load, spreading electricity production over the day, reduces the grid load and lowers costs.

“The key elements in energy generation by roof-integrated-solar systems are surface area, orientation and tilt angle, as well as ideal exposure,” said Hachem.

That means that the surface used for the integration of the solar technologies should not be shaded.

“Surface area can be tricky because it is largely dictated by the building geometry,” she said.

The EnergyPlus energy simulation tool is used to assess energy performance.

Early results suggest energy generation depends heavily on the size of usable roof area, affected by both shape and orientation.

Solar thermal collectors and photovoltaic panels are built into the roof to reduce costs and optimize energy supply.

Modifying the traditional rectangle home to adopt a more sophisticated shape could mean an increase in the total perimeter of the building envelope — an issue that could be addressed by building smaller houses.

“Canadian houses are usually very large, resulting in most of the cases, in a large percentage of unused space, and with large energy bills,” said Hachem.

A shift in materials ratio — wood or other opaque materials to glass — would depend on façade orientation and surface area.

Generally speaking the largest area of windows would appear on the south-facing façades.

In a townhouse neighbourhood, assuming that the rows are south-oriented, shade should be avoided on the south-facing façades and roofs, she said.

“Therefore, a distance depending on the height of the buildings should be kept between the rows,” she said.

In neighbourhoods where high density is mandatory, Hachem suggested attached housing, which would decrease energy consumption and provide more rooftops for solar technology integration, compared to dense detached configurations.

The study is focused on two-storey residential units with 120-square-metre total area, but Hachem said the results could be applied with suitable adjustments to any building project.

Her PhD is expected to be completed in 2012, but the research is expected to continue beyond that time.

ASHRAE awards 10 to 25 Grant-in-Aid grants annually to graduate students pursuing research in ASHRAE-related technologies.

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