Hot Water Heaters

We are using tankless hot water heaters for our house.  We actually have three:  two in the main house and one for the studio.  We aren’t installing hot water in the outdoor bar area (I hear it’s traditional that you don’t have hot water at a bar sink…who knew?!).

Gas tankless hot water heaters are the most efficient to use, heating water only when the appliance senses water flowing through it.  And while the heater gives a huge blast of gas-powered flame to the water as it flows, you’re not paying to keep a 50 gallon tank of water hot 24/7. 

Our house design is very conducive to efficient use of tankless heaters.  The north side of the house accommodates the master bath (downstairs) and the kitchen (upstairs).  The south side of the house accommodates two guest baths and the laundry room.  By installing two heaters – one on the north wall and one on the south wall – we minimize the length of the pipe runs from heater to end-use faucet or appliance.  LEED awards points (in the Energy & Atmosphere category) for keeping the pipe runs under 20 feet for 1 story homes or 20 feet + ceiling height for 2 story homes.  So for our 2 story home, we’re allowed runs of 29 feet.  Our longest run is approximately 20 feet.  The photo above is of the interior/backside view of one of the tankless heaters.  Ours install on the outside of the house…and you’ll note that it backs up into the master wet area that houses our tub and showers.  We’re very close to our hot water source…which will be nice on those rushed or chilly mornings.

We’re reusing one of the hot water heaters from our old house.  We loved it, had absolutely no issues with it and would recommend it to anyone.  It is a Noritz.

Energy & Atmosphere (LEED EA Category)

The Energy & Atmosphere category can be a little confusing.  USGBC has created alternate paths to earning points for Energy & Atmophere.  Our Home Provider only supports the path that requires a rating using the HERS Index.  According to the government’s Energy Star website, a HERS Index is

a scoring system established by the Residential Energy Services Network (RESNET) in which a home built to the specifications of the HERS Reference Home (based on the 2006 International Energy Conservation Code) scores a HERS Index of 100, while a net zero energy home scores a HERS Index of 0. The lower a home’s HERS Index, the more energy efficient it is in comparison to the HERS Reference Home.

Each 1-point decrease in the HERS Index corresponds to a 1% reduction in energy consumption compared to the HERS Reference Home. Thus a home with a HERS Index of 85 is 15% more energy efficient than the HERS Reference Home and a home with a HERS Index of 80 is 20% more energy efficient.

Our preliminary HERS Rating is a 69.  Our rating could have been lower if it wasn’t for the number of windows and lights in our home.  When performing the preliminary rating (which is based off of plans and a conversation about design and use of the home), our Home Provider also gave us a list of things we could do to get a better rating.  We have agreed to incorporate better insulation in a few areas and to upgrade our windows in the front window tower.  But upgrading the tankless hot water systems would cost significantly more so we chose not to do that, neither did we choose to reduce the window-to-wall ratio.  We have a ratio of 30% now, and to get a six-point decrease in our HERS Rating we’d have to reduce it down to 22% – given the fantastic design of the house, that just wasn’t feasible (although we did go through the exercise to see if it was possible).

One more point to make about the HERS Rating:  they take into account not only how the house is being built (windows, doors, insulation type, HVAC type, construction methods, etc), they take into account the heat gain of the items in the house.  So every appliance or component that emits heat is measured – refrigerator, stereo, computers, etc. – because the heat that they generate has to be countered with cool air, which requires electricity, which is energy, which is what we’re trying to use less of.

While the EA Category for us focused primarily on the HERS Rating, there are a few other areas where we could gain points.  We obtained points for our hot water distribution system.  While we didn’t upgrade to the super-duper tankless heaters, we are using tankless throughout the house.  And we got points not only for the tankless heaters themselves, but for the fact that the heaters are located close to the faucets they serve (no more than ~30 linear feet).  The idea being that when you turn the hot water on in the shower, you don’t waste water or energy waiting for hot water to travel the pipes to the shower head.  We also get a point for insulating all hot water pipes 90 degree bends…apparently that’s where hot water pipes lose most of the heat of the water.  We also got points for refrigerant management.

To get a good sense of the practices that you will end up using regardless of whether you use a HERS Rating or not, look at the alternate path in LEED.  The following categories are addressed, and we could have gotten a good number of the points in that path.  Let me know if you have any questions about these categories:

  • Insulation
  • Air Infiltration
  • Windows (we struggled with windows and I’ll blog about them separately)
  • Duct Tightness
  • Space Heating & Cooling
  • Domestic Hot Water
  • Lighting
  • Appliances
  • Renewable Energy 

Pointwise, the EA category is our weakest, again mostly due to the amount of windows and lights in the house.  We may earn a few more points if we get a better final HERS Rating, but the category will still be our weakest.

Energy & Atmosphere expected points:  18 out of a possible 38.