Enclosure Driven Design Approach – On the heating and cooling side, the Deep Energy Retrofit design is enclosure driven. A building’s enclosure is made up of the six sides of the building – the roof, the walls (including the windows and doors), and the foundation. Our design goal is to drastically reduce Castle Square’s heating and cooling needs by focusing on enclosure improvements first.
This means we focused our design to 1) increase the insulation (the R-value) and to 2) substantially reduce air leakage through extensive air sealing. Only after the building’s heating and cooling needs were made as small as possible through enclosure improvements, did our team then match the remaining load with tiny appropriately sized high efficiency mechanical heating and cooling equipment.
The result of this approach is staggering. Air sealing and insulation result in a 61% reduction in heating needs and a 68% reduction in cooling needs.
An enclosure driven design approach also has advantages in terms of building longevity and reduced operations and maintenance. If designed and constructed effectively, enclosure improvements (with generally minimal maintenance) can last the life of the building. Savings from enclosure improvements are, in effect, permanent.
In contrast, a design philosophy that focuses on complex heating and cooling equipment and renewable energy alone, can be more prone to having problems over time. Heating, cooling, and renewable energy equipment generally lasts only about twenty years. This means that energy savings from equipment alone may be less permanent.
There is also more room for human error in the operation of mechanical equipment. For example, if staff do not know how to maximize equipment operation, mechanically-driven energy savings may never be fully realized. This is a common problem, because even if some staff are well trained at first, knowledge can be lost due to frequent maintenance staff turnover.
For these reasons, our team focused on enclosure improvements as the driver for energy savings, with tiny high efficiency mechanical equipment sized to match the small building loads. This is not to say that we did not use renewable energy or the most efficient boilers at Castle Square. We did. However, first, we focused on decreasing the heating and cooling needs as low as possible through insulation and air sealing. Then we matched the remaining energy needs of the building with efficient heating and cooling equipment and solar hot water.
Why Not Use More Renewable Energy Instead?
The only renewable energy system we use at Castle Square is solar hot water. Unfortunately, renewables such as solar photovoltaics and wind were not feasible due to physical site constraints, like too much shading and not enough wind.
In a Deep Energy Retrofit Design, renewables are not the main energy savings feature (the super insulated shell is). Renewables are intended to augment energy savings, not create most of the energy for the building. This is because renewables (solar thermal, solar photovoltaics, wind, etc) cannot generally provide enough energy at a given property to make enough of a difference. For example, the roofs can only fit so many solar panels. Generally, insulation and air sealing is also cheaper than creating the equivalent amount of energy from renewables.
So at Castle Square, we invested our money in insulation and air sealing first. Then we reduced our energy load further by using solar thermal. At Castle Square, renewables are the icing on the cake. At Castle, like at most buildings, it is not economically or physically feasible to make renewables the cake itself.