Home Heat Loss: A Complete Guide

How and where does home heat loss occur, how to fix issues, and how heat loss mapping can help

Understanding Home Efficiency

Drafts, uneven temperatures, and high bills are signs of an inefficient home. In many cases, heating systems work overtime to compensate without making a home comfortable and still allowing heat and money to escape.

Homes can be kept warmer in the winter and cooler in the summer by adding insulation, sealing air leaks, improving windows and doors, and upgrading mechanical systems. These upgrades can lower utility bills, while making homes more comfortable.

In this guide, we’ll help you understand how your home works, how air moves around your home, common places you lose heat, and provide some quick tips to improve your home’s energy efficiency.

Table of Contents

How Your Home Works

What is the building envelope and why does it matter?

When addressing home heat loss, you first need to consider the building’s envelope and where it might be letting heat escape. Think of it as the shell of your house, separating the indoors from the outdoors.

The building envelope consists of doors, windows, walls, roof, and basement or crawlspace. To maintain a comfortable and efficient living space, it must effectively control the flow of heat, air, and moisture in and out of your home.

Heat Flow

Heat moves from warm to cold areas through materials (conduction), liquids and gases (convection), or in a straight line heating anything solid in its path that absorbs energy (radiation). When minimizing heat flow, focus on insulation in the home’s roof, walls, floor, and basement and avoid gaps in the insulation or building envelope (thermal bridging).

Air Flow

Air leaks through gaps in the building envelope when there is a difference in air pressure between the inside and outside of the home. When minimizing air flow, focus on leaky windows and doors, poor sealing around plumbing and electrical penetrations, and consider adding wind barriers under the exterior wall finish.

Where is air leaking from my home?

Homes can have air leaks through different points, causing energy inefficiency and increased heat loss. Common areas for air leakage include gaps around windows and doors, cracks in walls and floors, unsealed ductwork, electrical outlets, and plumbing penetrations.

Attics, basements, and crawl spaces can also contribute to air leakage if not properly sealed. These leaks allow conditioned air to escape and outside air to enter the home, resulting in higher energy bills and reduced comfort. Sealing and insulating these areas correctly is crucial to minimize air leakage and improve the energy efficiency of your home.

Did you know? Air leaks can be a significant source of heat loss. In a typical house, all of the holes and gaps can add up to an opening equivalent to a medium-sized window left open 24 hours a day.

A graphic of a cross-section of a home showing 11 different locations to check for air leaks
Source: Natural Resources Canada
Here are some of the key areas of your home to check for air leaks.
  1. Attic hatch
  2. Ceiling penetrations into the attic
  3. Door
  4. Exhaust vent
  5. Mail slot
  6. Sill and header
  7. Service entry
  8. Floor Drain
  9. Foundation crack
  10. Electrical Outlet
  11. Window
  12. Chimney

Moisture Flow

Moisture originating from the outside (precipitation or flooding) or inside (water vapour from occupants) can damage your home and impact its durability. When minimizing moisture flow, focus on drainage around the home, the vapour barrier on the warm side of the insulation, and limit moisture created indoors.

How much moisture is produced by indoor activities?
Moisture Produced (Litres)

Cooking - 3 meals daily for a week


Bathing - 0.2L per shower or 0.05L per bath


Washing Clothes (per week)


Floor mopping per 9.3 square meters (100 square feet)


Normal respiration and skin evaporation from occupants


Source: Natural Resources Canada – Keeping the Heat In

Did you know? Humidity levels should be between 20% and 40%. 20% and above can prevent dry, sore throats, and make the air feel warmer and more comfortable. Levels above 40% can cause frosting and fogging of windows, staining of walls and ceilings, peeling paint, mould growth, and odours.

How much insulation do I need?

The appropriate amount of insulation for your home depends on factors such as your location, its climate, and the materials used to build your home.

The total number of Heating Degree Days (HDDs) will also affect insulation requirements for your home. A heating degree day (HDD) is a measurement that helps quantify the amount of heating required to maintain a comfortable indoor temperature in a building during the colder months.

The cumulative heating degree days over a period of time provide an indication of the heating demand and help in estimating energy consumption and determining appropriate heating system sizing and insulation requirements.

To determine the optimal insulation thickness, consider consulting insulation R-value recommendations tailored to your specific region in Canada or the US. These tables, pictured below, take into account some of these factors to make better recommendations about the R-value insulation required for maximum comfort. 

A map of Canada that displays the total Heating Degree Days across different regions

Canada Insulation Map: Heating degree-day zones (HDD) and recommended minimum insulation values.

Zones by HDD: A) up to 3500HDD, B) 3500-5000 HDD, C) 5001-6500 HDD, D) more than 6500 HDD. Source: Natural Resources Canada – Keeping the Heat In

How much insulation should you add to different parts of your home if you live in Canada?

The R-value insulation recommended for your home will vary depending on where you live. The table below provides recommended R-values for different parts of your home and for different zones in Canada (US further below). All values given are in RSI (metric system)

RSI Insulation Value Table - Canada, Zones A-D
House Component
RSI Value – Zone A
RSI Value – Zone B
RSI Value – Zone C
RSI Value – Zone D











Roof or Ceiling










Did you know? Insulation is labelled with an RSI or R-value. Both rate the material's ability to resist heat flow. The higher the value, the slower the rate of heat transfer through the insulation.

How much insulation should you add to different parts of your home if you live in the US?

Similar to Canada, your insulation requirements will vary depending on where you live. The US also has ‘zones’ to help you determine the amount of insulation required. 

Insulation Zone Map of the US

US Insulation Map: Recommended insulation levels for retrofitting existing wood-framed buildings.

Zone 1 is in Florida, with zone numbers increasing with latitude up until Zone 7, in the Minnesota and North Dakota region. All of Alaska is in Zone 7 except for Bethel, Dillingham, Fairbanks, N. Star, Nome, North Slope, Northwest Arctic, Southeast Fairbanks, Wade Hampton, Yukon-Koyukuk. Zone 1 includes Hawaii, Guam, Puerto Rico, and the Virgin Islands. Source: Energy Star – Recommended Home Insulation R-Values.

The table below provides recommended R-values for different parts of your home and for different zones in the US. All values given are in R-value (imperial system).

R-Value Insulation Value Table - US, Zones 1-5
House Component
R-Value – Zone 1
R-Value – Zone 2
R-Value – Zone 3
R-Value – Zone 4
R-Value – Zone 5

Attic (Uninsulated)

R30 – R49

R30 – R60

R30 – R60

R38 – R60

R49 – R60



R13 – R19

R19 – R25

R25 – R30

R25 – R30

Attic (3–4 inches of insulation)

R25 – R30

R25 – R38

R25 – R38


R38 – R49


Whenever exterior siding is removed on an uninsulated wood-frame wall:

  • drill holes in the sheathing and blow insulation into the empty wall cavity before installing the new siding, and
  • Zones 5-8: Add R5 to R6 insulative wall sheathing beneath the new siding.
  • Zones 3-4: Add R5 insulative wall sheathing beneath the new siding.

Whenever exterior siding is removed on an insulated wood-frame wall:

  • Zones 4-8: Add R5 insulative sheathing before installing new siding.

10 Quick Tips to Save Energy at Home

Icon of a hand and a coin

Explore resources in your area:

If available in your area, take a look at your home profile to discover potential heat loss areas and see how your home compares to similar homes in your city. Once finished, contact your local utility or government agency to learn about rebates that may be available to help you save energy.

Icon of a home with a magnifying glass inspecting it

Complete a detailed home evaluation:

Contact a local energy advisor to get professional insight into your home's energy performance. They will complete a detailed audit of your home to help you identify problem areas and recommend the next steps for action.

Icon of cross-section of home showing pink insulation inside

Upgrade insulation:

If your home is more than 15 years old, it is likely under-insulated compared to current standards. Look for opportunities to add insulation to your attic, walls, and basement. Increasing your home's insulation is one of the fastest and most cost-effective ways to reduce energy waste.

Icon of a thermostat showing tempertaure of 22˚C

Install a programmable thermostat:

Stop heating an empty or sleeping house. By installing a programmable or smart thermostat, you can automatically adjust the temperature and save up to 15% on your heating needs. Additionally, avoid heating unused rooms by closing vents and doors.

Icon depicting attic hatch open

Eliminate drafts around attic hatch:

Even if your attic is already insulated, the pull-down hatch is often left without protection. A surprising amount of heat can escape through those leaky doors. Make sure this area is insulated and gaps are sealed.

Icon depicting an electrical outlet

Seal electrical outlets:

Place your hand in front of an outlet on a cold day. If it is cold, carefully remove the cover after turning off the power to insulate your outlets. Use caulking to fill gaps around the outside of the box and insert a foam gasket specially made for insulating outlets.

Icon depicting plumbing pipes

Seal plumbing penetrations:

The places where pipes enter and leave your living space need to be sealed with foam or caulk - builders sometimes neglect this step. Check in your basement ceiling and inside cabinets, as well as exterior walls.

icon depicting a window

Caulk around window frames:

Windows can be the weakest points in your home's envelope. Remove old cracked caulking and replace it with fresh caulk. Combined with lined drapes or blinds, this will address one of your home's greatest points of heat loss. Also consider replacing old windows with newer, energy-efficient ones.

Icon depicting a door

Adjust door thresholds:

Can you see daylight under exterior doors? Some thresholds are adjustable with screws: turn them counterclockwise to close the gap. You could also buy or make a “draft snake” to place across the draft at the bottom of a closed door. Also, check the weatherstripping around your doors and replace if it looks worn.

Icon of a fireplace

Replace your flue damper:

Most of us know to close the damper on our fireplace whenever it is not in use to reduce heat loss through the chimney - but a lot of warm air still escapes. Some dampers fit poorly and provide little protection from draft; a snug-fitting damper may save 8% of fuel costs.