The following post in an excerpt from CSE live.
By David Sellers
Ask yourself if there is any problem with your home that has bothered you. For instance, is there a room that is uncomfortable relative to the others? Is the HVAC system noisy when it runs? Do you wish that your utility bills were lower and is that a realistic wish? As a side note, I suspect that everyone wishes that their utility bills were lower, But, for instance, my worst case heating bill is about $50 for gas. That’s probably because Kathy (my bride) and I have a small house, reasonably tight and well insulated in a mild climate with a high efficiency gas furnace; probably not much that I can do to meaningfully reduce the bill. That doesn’t mean there aren’t meaningful things I can do to improve the way I use gas, which is a non-renewable resource that generates atmospheric carbon when I burn it. But, given the modest cost (currently) to heat my home, the perspective driving the desire to improve things will need to be more holistic rather than economic - a lesson I think for our current bottom line driven society. Anyway, the point of these questions is to find out if there is something you want to target a test at. Probably 50% or more of the tests performed by commissioning providers in the field are targeted at solving a specific problem or verifying a specific level of performance. But, that doesn’t mean you can’t learn something if you don’t have a problem to target with your test. You can do an information gathering test and find out exactly how your house performs. Here are some ideas that come to mind.
Deploy a data logger outside that tracks relative humidity (RH) and temperature and then deploy several loggers inside tracking the same thing along with maybe some indication of occupancy like light level or the operation of an electric light, and maybe one that tracks furnace operation. Then plot concurrent data to see how the environment inside your house responds to changes in the ambient environment and the use patterns. For instance, what happens to the RH inside when you take a shower? At night, if your furnace has night set-back, how fast does the temperature in the house drop off relative to how fast the temperature outside drops off. How about RH? How does RH compare to specific humidity or dew point which is a more absolute indication of moisture level? (Some data loggers will calculate dewpoint an specific humidity basedo on the parameters they measure. But if not, you can figure it out from a psych chart). How does absolute humidity inside and outside compare and track?
Deploy a current or kW logger on your power panel and on some critical (large) loads like the your dishwasher or your washer and dryer or your water heater (if it’s electric) and plot concurrent data to see how much of an impact on total load each appliance has. Add more loggers to other circuits serving light loads and plug loads to see how you use energy in your house. Only do this if you feel comfortable putting CTs on your circuits or if you know someone who is an electrician or who is comfortable doling that for you if you aren’t. (Electricity, even at the voltages we use in our homes can be dangerous if you don’t know what you are doing or aren’t comfortable working around it. Never do anything with electrical wiring that you are not comfortable doing and/or have not been properly trained to do.)
Put a logger on your furnace to measure differential temperature and pick up fan operation. Or deploy or add another one to monitor filter pressure drop. Deploy another outside to track ambient conditions or download the data from the web using one of the techniques/sites discussed in the Functional Testing Guide. Use a rotating vane anemometer to traverse your return grilles and get an idea of air flow. Then, simply log the operating of the system and see what it tells you. For instance, how does the actual capacity of the furnace compare to the rated capacity? How does the cycling time vary with changes in outdoor temperature? If you have a night set back thermostat, how does that impact the operation of the system vs. the way it operates once the house is warmed up or, at night once the house has cooled off to the set-back temperature? How long does it take your filter to load up? (Generally, filters should be changed on pressure drop, not appearance or time ).
Use the rotating vane anemometer to traverse your return grills and get a feel for total system flow. Then traverse your supply grills and see how the flow is distributed. Is it fairly uniform on a cfm per square foot basis, or are their areas with a lot of air and areas with less? If the distribution is not uniform, is that because of the loads in the areas served? Or does your system need balanced? (Maybe there is a reason that one area is always hot or cold!)
If you have an electric water heater log its power consumption and then use that data to compare what would happen if you heated your water using one of the heat pump based technologies that’s out there or using a conventional gas water heater or using one of the high efficiencyinstantaneous type heaters. Look at both the source and site energy implications and the atmospheric carbon implications.
Some of you may be thinking “that’s all well and good, but what if I don’t have a data logger?” If you live in California in one of the public utility service districts, you are in luck. You can borrow a logger from the Pacific Energy Center’s tool lending library . This is (as us 60’s generation folks would say) a “free to the people” resource that is available to you as a utility customer. Many of the private utilities in California and other states offer a similar service. Another option is to simply buy a logger. For under $100, you can be off and running. For about $300, you can be logging just about anything.
