Home is located in NE Pennsylvania. Some details:
- Runs entirety of the home's footprint (~1000sqft)
- Approximately 5' high
- 1/2 (2.5') Below grade
- Vapor barrier on the floor, sump pump
- Cinder block walls, piers
- Incoming water pipe, water heater (40gal tank, electric), and water piping for home is in crawlspace
- Has vents to outside - closed in fall/winter (condensation not an issue in NE PA)
Currently I have an electric heater hanging from the rafters set to about 48º that is thermostatically controlled (this one: https://www.amazon.com/gp/product/B0000AXEZV/ ). This heats the crawlspace during the cooler months to maintain an above-freezing temperature.
The home is occupied only on the weekends in the winter, and empty during the week. While unoccupied I turn off the incoming water with a valve, and drain the upstairs completely. The downstairs (just above the crawl space) is not drained. Rooms without plumbing are shut, rooms with plumbing have baseboard heaters set to 42ºF with the doors/cabinet doors opened.
(some details about inside: there is a single mini-split unit in the main area of the home set to 48ºF that maintains the temperature in the entirety of the home while unoccupied. Also inside is a newly-installed propane ventless fireplace with millivolt remote and thermostat feature - minimum setting of 45ºF. (I haven't tried using this to maintain non-freezing temps yet - not sure how I feel about having a fire burning in an unoccupied home).)
During January/February, 2019, while unoccupied the temperature would approach 0-15ºF, and the total daily energy usage would approach 60-100 kWh. Taken over a month at about $0.13/kWh, and an average usage of 80 kWh, this is about $10/day to heat the the crawlspace to 48ºF.
Fuel options in the home:
- Liquid Propane - 120 gal tank exposed to elements
- Electric (120v or 220v)
Here are some ideas I've considered to reduce crawlspace energy usage:
- Heat tape on the pipes (plugs into 120v, heats only the pipes)
- Install foam insulation board between piers below house and reduce the footprint needing heat (the pipes and water heater are on the front half of the 1000 sqft crawlspace - could reduce "envelope" to 500sqft)
- Install liquid propane heater (I've read about condensation issues with propane heaters in crawlspaces - and combustion danger)
- Drain the pipes (this is inconvenient because we use the house on the weekends)
Does anyone else have a similar plumbing situation / weather / occupancy rate in their home and have opinions on the suggested solutions for reducing energy usage while making sure the pipes don't burst when the temperature drops outside?