Shouldn't I Uber Insulate and Super Air Seal My House?
Not likely, is the quick answer.
Yes that's right, expensive super insulation and super tight air sealing isn't necessary. They may be good ideas for comfort or air quality but they are not the best economical options for Net Zero Retrofits.
In fact only very poorly insulated areas of your house require additional insulation and poorly sealed houses (think drafty farmhouse level of leaking) require additional sealing.
Consider this graph showing the energy rate costs for various fossil fuels, renewable fuels and energy conservation measures.
The fossil fuels costs are shown in red, renewable fuels costs in green, electricity and an electrically driven heat pump and electric resistance heating is in blue as they both have renewable fuels (hydro, wind, solar) and fossil fuel (natural gas) components and lastly energy conservation measures are in yellow. The list of energy conservation measures is not exhaustive but shows the measures we are most likely to find in the houses we analyze. Note that the fossil fuel costs are highly dependent on the region one lives in and varies somewhat by the time of the analysis. These figures are for March 2020 at Ottawa, Ontario, Canada.
The energy conservation measures cost or Levelized Cost of Energy Conservation (LCOEC) is calculated by taking the overall costs of the initial conservation measure and it's maintenance costs in dollars (CAN) over the life of the measure and dividing these by the total amount of energy conserved during the life of the measure to produce a $/kWh figure that can be compared to the fossil and renewable fuel costs. These costs vary marginally for different regions and somewhat by manufacturer and contractor.
Similarly the cost of solar power is calculated by taking the overall costs (initial and maintenance) of the solar power collection equipment over it's life and dividing it by the power (in kWh) to produce a $/kWh figure that can be compared to the fossil and renewable fuel costs. Solar power costs varies somewhat by manufacturer, contractor and region.
The Domestic Hot Water/Solar combination (DHW HP/Solar), Ground Source Heat Pump/Solar combination (GSHP/Solar) and Air Source Heat Pump/Solar (ASHP/Solar) costs are the costs associated with the combination of a heat pump powered by electricity and the electricity offset by solar power from on site panels. Note that the solar panels do not directly power the heat pump. As the sun doesn't necessarily shine at the exact moments we need the power for the heat pumps (think of overnight) the solar panels are sized to create the equivalent amount of energy required to power the heat pump over a year. So when the sun shines solar power decrements the electricity meter and overnight or on cloudy days the electricity is taken from the grid and the electricity meter increments. At the end of the year the solar panels are sized to make the electricity meter net out to zero. This arrangement is called Net Metered solar power or Net Metering. Heat pump costs vary significantly by manufacturer and model. We do studies to determine which is best for you. See this webpage.
Here are the Important Observations (in Our Region);
Natural Gas is the cheapest fossil fuel and the reason that most everyone with access to natural gas chooses natural gas.
Heating in the rural areas not supplied by natural gas is typical supplied by fuel oil, propane or electric resistance. There are excellent cost savings by switching rural heating to heat pump or heat pump with solar power.
Space and Domestic Hot Water Heating with heat pumps in combination solar power are in the same order or slightly less expensive than natural gas in Ontario (and many other jurisdictions).
Retrofitting your house with high insulation levels (shown by Insulate Above Code Levels) is more expensive than heating with an heat pump offset by solar power. Or in other words, you are better off from an economical stand point to install more solar panels and heat pump capacity than to highly insulate (exterior walls and attics). Also this level of additional insulation (i.e. adding 4" of loose fiber insulation to your insulated attic attic or 2" of continuous rigid board foam insulation to your walls) is more expensive than adding additional heat pump and solar power. You may like to add these levels of insulation for comfort but not for economical reasons.
Passive Haus levels of insulation (R30 more than the "Insulate above Code Levels") are not shown as the scale doesn't go that far to the higher cost level but one can conclude that it is isn't an economical measure.
Also not shown are much higher levels of sealing (less than 3 Air Changes Per Hour). The problem with levels below 3 ACH is that humidity levels begin to rise which then requires a Heat Recovery Ventilator (HRV) to be installed. HRVs are not 100% efficient machines and require the same levels of fresh air supplied as the sealing prevented. This results in no net energy savings gains but additional significant costs for the HRV. Again this measure is not an economical measure. One may do it for air quality reasons but not for economical reasons.
Solar power electric supply is less expensive than utility supplied electricity.
Given these observation we generally choose to plan to retrofit your house with;
Solar power to offset your existing energy load.
High value energy conservation measures where appropriate.
Move your space and domestic hot water heating to heat pump heating.
Offset the additional electrical energy required by the space and DHW heating with solar power energy.
See this webpage for our method.
See our fee webpage to discover the costs for Net Zero and/or fuel transition planning.