We have hired a mechanical engineer to design the air treatment and systems in the house we are building - which if you have been reading out blog you know happens to be one for us personally. This adds a few thousand dollars to the cost of the build, and while not required by either passive house or by building code, it is a logical step to take.
In a typical house that is built to minimum building code, The HVAC contractor installing The equipment is the one who generally will “design “the system for the house. These systems are basically just air movers, with heat or cooling capability. It is based on the cubic footage within the house, and typical air flows needed in areas. There is not a lot of designing that actually goes into it, at least not specifically designing the airflow.
Another aspect of a typical code compliant house is fresh air intake and air filtering. Most times fresh air intake is not controlled, nor is it handled in any special way. There usually is a small fresh air intake that allows the HVAC units to simply draw in some fresh air, and mix it with the air that comes back in a return of the house.
Because the passive houses are built and engineered to such a tighter standard, it really isn’t reasonable to expect that an HVAC contractor is going to be able to design the necessary system. And with the house being built so much tighter, you have to make sure that the air quality in the home is managed and engineered, much more than your typical home.
This is a long way of saying we needed a mechanical engineer to make sure that the house will have fresh quality air. In another blog I will discuss the different systems that are involved with the HVAC for a passive house.