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Sustainable Building Essay 4

April 1, 2011

Rocky Ridge Retirement Residence Energy Analysis

pRRoject in bRRief

The RRRR (Rocky Ridge Retirement Residence) is a two story multi-unit retirement home located in Calgary, Alberta in the very northwest tip. It sits in a typical sprawling neighborhood next to a community center but otherwise isolated from anything within walking distance. Culturally this location is lacking as there appears to be no center to which the inhabitants can connect to the community as it goes about its daily operations. The community center looks like it’s only for “special events” and otherwise there appears little thought towards “community”.
From the satellite images it looks as though it sits on a high water table with rolling hills and little tree coverage. The site will experience typical weather regionally referred to as a prairie steppe climate. It will receive good sun year round with cold winters and consistent winds. Summers are reasonably dry and winters are often interrupted with warm Chinook winds from the west, which is also the direction of the prevailing winds. There was no current human use for the site though it probably was a nice green space. The building is sited with its longest walls about 20 degrees off a full east/west exposure.
Some of the sustainable goals identified for the building would be to make the building a “community center”. A place that the community could be drawn into on a regular basis and the retiree’s would continue as part of the community rather than withdraw from it. Making use of the community center next door could be integrated and would be encouraged. The building itself lends a challenge to making use of solar but could it could be integrated, though architecturally it lends many challenges. Having a large human capacity, waste heat recovery will be explored. Green roofs and solar walls will be considered. Also the effect the building and its coverage will have on the local water behavior and environment will be looked into and how design could lower negative impact, local material will be looked at for building material and landscaping will be examined to produce a low maintenance site that works with the building for solar shading.

The Four R’s and Energy

The siting of this building makes it difficult to configure for energy optimization. The south exposure is a short wall though it sits high geographically as it’s on a hill. It has good window coverage but the windows go into individual suites so only they benefit from good winter solar gain. Passive heating is out of the question and passive cooling is questionable though could be attained. The roof is a combination of pitched roofs with small flat roofs connecting them making it difficult to have a cost effective solar PV installation and nearly impossible to have a solar thermal array. Wind power is not an option as it’s a residential area leaving geothermal heating and cooling its best “green” energy source.

GeotheRRRRmal

Geothermal heating and cooling is a proven technology that uses the ground as both an energy source as well as an energy sink. The idea is to use electricity to condition the medium that in turn conditions the living space. The extra added bonus is to pick up extra energy in the process for “free”. Often systems run at 300% efficiency, meaning for every 1 unit of energy used 2 more units of energy are gained in the process and used to condition the space. (actual efficiency will vary with region, installation and distribution system). A geothermal system works by circulating fluid through a “field” which can be vertical wells drilled down into the earth, horizontal runs laid out in trenches or loops run into a body of water. This fluid either picks up thermal energy or sheds it, depending on the load demand of the building, either heating or cooling. The fluid then travels back to the heat pump through a header that connects all the loops or wells. The heat pump is the main component of the geothermal system, it is where the energy is either “concentrated” to heat the building or rejected to the field loop to cool the building. It does this through a compression cycle exactly like an air conditioner does except that it can switch between cooling and heating. In a water to water heat pump the energy is transferred to/from the field to a hydronic system, meaning that it is distributed via another fluid, either to radiant floors or through fan coils or baseboards. In a water to air heat pump the energy is transferred to/from the field directly into an air stream that is ducted into the conditioned space. At The RRRR we would use a water to water heat pump that would couple into their hydronic system that distributes throughout the building to individual fan coils in each unit. From the site knowledge we do have it looks as though there is a high water table. A high water table will increase the amount of exchange we can get from the ground and will reduce the amount of wells that need to be drilled. This will save on installation costs making for a faster payback. Utilizing a water to water system is more efficient than a water to air system air hydronic systems are more efficient at distributing energy, also making for a faster payback. Geothermal systems are very low in maintenance needs. The geothermal system itself would have no filters that needed to be changed making for lower maintenance costs. In fact there is very little to the geothermal system at all that needs attention, and for a small cost could be monitored remotely.

Waste Heat RRRRecovery

Being a high occupancy building I anticipate that there will be a large amount of water usage. Taking into consideration laundry, bathing, showering, human fecal matter and pool facilities there will be a considerable amount of waste energy going down the drain. I propose a geothermal coupled waste heat recovery system. During the summer months the geothermal system would cycle through the recovery unit and shed the waste heat into the earth around the field, in essence, charge it with energy for the longer heating season that Calgary experiences. In the winter the heat pump would directly take the heat from the recovery unit and transfer it into the distribution system. This allows the heat pump to operate at even a higher efficiency than a standard earth coupled geothermal system while at the same time recovering energy that would just be “flushed down the toilet”. Waste heat is one of the largest parts of efficiency loss in a building. We spend tons of money on energy systems and building envelope, then literally flush energy down the drain. I say why not use the energy system to stop this!

Heat RRecovery VentilatoRRs

As for air distribution throughout the building I propose a large heat recovery ventilator (HRV). Fresh air would be brought into the HRV and preconditioned through an exchanger with conditioned but stale air exiting the building. I also propose using the hallways as unducted return air spaces to reduce the amount of material used in the system. This way we have fresh air circulating throughout the building maintaining a good indoor air quality.
In conclusion, though there isn’t much room on this building as it is without making large structural changes or moving it to another site and swiveling it to optimize it for passive solar capabilities, there are a few things that could be done, like the geothermal and waste heat recovery systems. I would also venture, budget permitting, some solar power production, whether on the south exposure or placed throughout the building on the flat roofs, or if possible, on the pitched roofs. The building offers some challenging criteria to get an energy system that works, but I believe the best possible scenario is the one presented here.