- The high efficiency heating equipment is expected to drop the building’s heating needs by another 10 percent. Insulating the pipes, combined with high efficiency boilers with indirect hot water heaters, is expected to drop hot water usage by 41 percent. In a typical leaky and poorly insulated building, big inefficient heating and cooling equipment is generally used to compensate for heating or cooling loss. A super insulated and air sealed building requires only a fraction of the energy to heat and cool. Tiny efficient equipment can be used to meet remaining heating and cooling needs.
Heating and Hot Water
Boiler Efficiency
The new high efficiency boilers at Castle Square have two distinct advantages over the old boilers, which had an efficiency rating of roughly 70 percent. First, the new condensing boilers capture heat that was previously lost up the flue when heat was carried away with the products of combustion. Second, the new boilers fluctuate their supply water temperature based on the outside temperature so that they only produce as high a temperature as is needed, resulting in an optimally efficient heating system. These new functionalities, coupled with a high performance boiler heat exchanger, yield an expected boiler combustion efficiency of over 94.5 percent.
Heating System Efficiency
The efficiency rating (AFUE) of a boiler is not the only driving factor in the overall efficiency of a heating system. Two more important influences are the layout of the distribution system and ensuring the equipment is sized to match the load, or heat requirement, of the building. In order to maximize the efficiency of the condensing boilers, the return water temperature from the apartments needs to be as low as possible. In order to achieve low temperature return water, and to conserve pumping energy, the flow rate to each apartment must be regulated so that each apartment gets the heat it needs without using any more flow than required.
Integrated Design – Right Sizing
A significant benefit of carefully calculating a building’s heating requirement and right-sizing the heating system, is that the heating system first costs are reduced. This savings in mechanical systems costs can be reallocated to help pay for things like insulation and air sealing that help reduce heating and cooling needs from the get go.
BEFORE – 70 percent efficiency atmospheric boilers are being replaced at Castle Square.
AFTER – 94.5 percent efficiency sealed combustion boilers are being installed at Castle Square. Only three of these tiny boilers are required, per boiler room, to serve the very small heating needs of 48 super insulated apartments.