In terms of passive house, Pretty Good House, or net zero energy house construction, how much should be budgeted for control systems that monitor and control humidity, CO2, exhaust, etc.?
lecolevielle2002
| Posted in Green Building Techniques on
I am asking because I’ve been advised that although a tight house may require smaller sized HVAC equipment, the high efficiency equipment are more expensive and there are expensive control systems not present in conventional house construction.
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Replies
Lecole,
I don't think you need any expensive control systems.
Temperature is usually controlled by a thermostat, which is a common part of most heating and cooling systems.
If your house is well designed, humidity will be controlled by your cooling system during the summer (which is controlled by a thermostat) and by your ventilation system in winter. Ventilation system controls are included if you have an HRV or ERV; if you have an exhaust-only ventilation system, you will probably need to buy a 24-hour wall-mounted timer.
For more information on ventilation systems, see Designing a Good Ventilation System.
I don't see any need for a CO2 sensor for most homes. You should have a CO (carbon monoxide) detector, however, regardless of whether you home is energy-efficient or not.
Thank you for the quick response, Mr. Holladay.
I had read the Designing a Good Ventilation System article. There seems to be a difference between continuously operating systems and systems that operate under the direction of one or more sensors. As a lay person, I could not tell whether the industry has determined a best practice as yet. From your response, it sounds like such complex systems may be appropriate in commercial construction, but perhaps less so in residential construction.
L'ecole Vielle
L'école vieille,
In general, I'm not a fan of ventilation systems that are controlled by sensors. Some people have decided to control their ventilation system by a humidistat. The problem with this approach is that your indoor relative humidity (RH) is likely to be 30% in winter -- that's normal -- and 60% in summer -- also normal. So you have to adjust your controls every spring and fall. Very few homeowners (a) understand why this is necessary, or (b) remember to perform the task.
The best way to control a ventilation system is with a 24-hour timer. If your house seems humid and smelly during the winter, you simply increase the ventilation rate. If the house seems too dry during the winter, you decrease the rate. During humid weather in the summer, it makes sense to decrease the ventilation rate. Or just leave the controls set at the same rate year round -- meeting ASHRAE 62.2 or somewhat less -- and forget about it.