Three topics
• The importance of measuring household
energy usage over time
• Known knowns, known unknowns, and
unknown unknowns
• What a house that’s part of the solution
rather than part of the problem should look
like in a decade or two…
The importance of measuring
household energy usage over time
Energy units
Unit
Fuel type
Btu content
Kilowatt hour
Electricity
3,413
Therm
Natural gas
100,000
Gallon
Heating oil
138,000
Gallon
Gasoline
125,000
Calculating energy usage
• Convert all fuels to Btus (British thermal units)
– Annual therms of gas x 100,000
– Annual kWh of electricity x 3,413
– Annual gallons heating oil x 138,000
• Add them all up to calculate total Btus consumed
per year
• Divide by square footage of the house and you
get Btu/sf/yr – an “energy score” you can
compare with other homes
• Track over time
122 pre-retrofit homes compared with 20 post-retrofit
pre-retrofitted homes
post-retrofitted homes
30
# of homes in each bin
25
20
15
10
5
0
0
2
4
6
8
10
12
-5
10,000 Btu/sf/yr bins
14
16
18
Average Rolling Primary
18,000,000
Finish renovation
16,000,000
14,000,000
Primary/person
Starting taking
measures to save
Forget to turn off the
gas fireplace pilot light
for the summer
My wife starts baking
her own bread
Realize we have
an energy hog
12,000,000
10,000,000
Start to get tired of the
austerity measures and
slack off a bit
Get an induction cooktop
and a new dishwasher
8,000,000
Daughter #2 to college
Daughter #1 to college
6,000,000
4,000,000
Daughter #2 to India for 4 mos.
2,000,000
Jan-04
May-05
Oct-06
Feb-08
Jul-09
Nov-10
Apr-12
Aug-13
Dec-14
Known knowns, known unknowns, and
unknown unknowns
• Things everybody already knows to do
–
–
–
–
–
Insulate and air-seal (but see below)
LED light bulbs
Getting rid of second refrigerators
Upgrade appliances
Thermostat set-backs for central heating & cooling systems
• Things we think we know to do but that don’t work as well
as we may want
– Replacement windows
– Basement ceiling insulation
– Running paddle fans during heating season
• Things we should be doing but maybe don’t know to
– Blower door as a diagnostic tool for all insulation projects
– Blower door as a diagnostic tool for most remodeling projects
– Testing range hood and bath fan exhausts to see if they’re
actually working as intended
– Commissioning central forced-air heating and cooling systems
LED light bulbs
Typical basement refrigerator
Impact of a new dehumidifier…
Blower door
What a house that’s part of the
solution rather than part of the
problem should probably look like in a
decade or two…
A 21st century home…
• Should not burn things indoors for heating,
cooking, clothes drying, or hot water
• That is to say, should be all electric
• Should be both as air-tight as reasonable (as
verified with a blower door) and have an energy
recovery ventilation system (ERV or HRV)
• Should have PV on the roof, if possible
• Should have more people in it than we currently
settle for