This entry was written by one of our members and submitted to our blog section. The author's views below are entirely his or her own and may not reflect the views of Green Home Guide.

OK, I'm back from getting the dimensions of Doe's house, enter all the information into EnergyPro, and do an initial calculation. It looks like the house as it is has a HERS of 147, which means that the model predicts that it will use about one and a half times as much energy as a 'reference home', which is this exact same home if it was built to today's energy code requirements and has by definition a HERS of 100. 147 is not too bad but way above what we want. Let's see if we can get it below 100.

I enter a selection of possible energy improvements into the software and recalculate. Great! There's a possibility of cutting Doe's energy use in half if all the improvements are done. Here's a screenshot of the EnergyPro run showing the percentage reduction in energy use that we will get from each of the measures:

  • air sealing the house,
  • adding ceiling insulation to R38,
  • insulating the floor,
  • a new 95% furnace with R8 ducts and 13 SEER AC, and
  • a new high efficiency water heater.

 

All of these together add up to a significant amount financially for most homeowners, as high as $20,000. But one of the strong reasons I want to suggest installing high efficiency condensing furnace and water heater is that condensing units draw their combustion air from outside. The combustion air vents in the doors and closet ceiling can be sealed up and there would no longer be all the air quality and heat loss problems that come from combustion appliances in an indoor closet. EnergyPro may model the percentage savings of the improved house but it can't show the increased comfort, how the HVAC system no longer constantly cycles on and off, how all the rooms are now an even temperature, how the owners are no longer breathing air from the crawlspace, and that there is no longer any possibility of carbon monoxide entering the house from the water heater's poor venting. All powerful reasons to do this whole package.

Plus, entering the Energy Upgrade California program should get the owners a $3500 check after the work is done and using our local property assessed program, the Sonoma County Energy Independence Program, means that John and Jane can finance the cost with only a few hundred in fees up front. If we can cut their utility bills in half (which currently average nearly $300/month), then their savings of $1800/year should cover the payments on the assessment and in 10 years, it's paid off. Sounds like this project is a win/win.

A few quick numbers from government research papers:

  • 40%+ of inside air comes from the crawlspace because warm air rises, drawing in crawlspace air through all the little holes in floors, also known as the Stack Effect. (anybody know the cite?);
  • 30%+ average duct leakage in the US, though my guess is it's in the 20s in California;
  • Far more people die of Carbon Monoxide poisoning in the US than are struck by lightning and CO causes 15,000 to 20,000 ER visits per year.

The recommendations going into my report:

  • Air sealing the ceiling, the floor, adjusting doors and replacing weatherstripping as needed to reach the minimum target of 1962 cfm50 (it's 3110 right now so that seems reachable);
  • Insulating the floor to R19;
  • Replacing the recessed ceiling fixtures or building boxes over them;
  • Blowing loose fill fiberglass into the attic to reach R38;
  • Replacing the FAU with a 95% condensing unit of much smaller size, with R8 ducts properly sized and sealed;
  • Replace the DHW with a 90%+ condensing unit and insulating all how water pipes;
  • Deal with the flooding issues in the crawlspace and cover the soil with a 12 mil vapor barrier.

 

Caution: numbers alert. FYI and if you are interested, 1962 cfm50 is the minimum that BPI currently allows without requiring mechanical ventilation, which is 70% of 0.35 natural air changes per hour with an n factor of 22.

Next, the report.