Quick answer
If your house feels cold, do not start by buying windows, insulation, a bigger furnace, or a stack of weather stripping.
First separate the problem into one of five paths:
- heating equipment - the system will not start, blows cold air, short cycles, or cannot maintain temperature
- heat distribution - one room or one floor is cold while the rest of the house is comfortable
- air leakage - the problem gets much worse in wind or you can confirm moving air at a joint
- cold surfaces / envelope heat loss - the thermostat reaches setpoint, but windows, walls, floors, or the lower level still feel cold
- bill problem rather than comfort problem - the house feels normal, but the heating bill jumped
That distinction matters because a 21 C thermostat reading does not prove every room and surface is comfortable, and a high heating bill does not prove the house suddenly developed a giant air leak.
Natural Resources Canada (NRCan) says uncontrolled airflow through the building envelope can be a major source of heat loss and identifies wind, winter stack effect, and exhaust/combustion equipment as pressure drivers. It also says that, in a typical home, about 25% of heat loss can be due to air leakage. That is substantial, but it is not a universal percentage for every house. See Keeping The Heat In: how your house works and Operating your house.
Health Canada’s current CO guidance says to leave immediately when a carbon monoxide alarm sounds and to call emergency services from outside. See Preventing carbon monoxide exposure.
Cold house diagnostic router
What kind of cold-house problem do you have?
This tool does not estimate heat loss, furnace size, insulation R-value, or a probability. It uses observable symptoms to choose the next diagnostic path.
Best next path
Start by separating heating, distribution, air leakage, and cold-surface problems
A cold house is a symptom, not one diagnosis. A few observations usually narrow the next step without guessing at equipment size or insulation values.
Check this first
- Confirm whether the whole house is cold or only one room, floor, window area, or lower level.
- Note whether the heating system starts normally, produces expected heat, and maintains the thermostat setpoint.
- Notice whether wind, deep cold, window proximity, or floor level changes the discomfort.
- Measure indoor humidity if dryness or condensation is part of the complaint.
ReadyHome next step
Do not shortcut this
Do not jump straight to new windows, insulation, or a larger furnace before identifying which system is actually failing.
This is a routing tool, not an HVAC diagnosis, energy audit, code check, combustion-safety inspection, or heat-loss calculation.
Why can a house feel cold when the thermostat says 20 or 21 C?
The thermostat measures air temperature at one location. Your body is responding to more than that one number.
Three things can make a room feel colder than the thermostat suggests:
- cold surrounding surfaces: windows, exterior walls, floors, and foundation walls can pull heat from you by radiation even when the room air is warmer
- moving air: a true exterior draft increases convective heat loss from your skin
- indoor downdrafts: room air can cool against cold glass, become denser, and fall toward the floor even when the window is airtight
That is why sitting beside a large cold window can feel uncomfortable without there being a crack around the sash.
ReadyHome’s weather stripping and draft guide goes deeper on the difference between air leakage, conduction, radiant discomfort, and cold-window downdrafts.
The useful rule is simple:
If something feels cold, confirm whether air is actually moving before you diagnose a leak.
Whole house cold vs one room cold
This is the fastest useful split.
Swipe across the table to compare all columns.
| What is cold? | What moves up the list | What moves down the list |
|---|---|---|
| Most of the house and the heating system will not start | Heating-system failure | Window replacement, room balancing |
| Most of the house while heat runs and indoor temperature keeps falling | Heating performance, severe weather, distribution, whole-home heat loss | One isolated door seal |
| One bedroom while the rest of the house reaches setpoint | Supply/return path, duct distribution, local envelope exposure | Total furnace outage |
| One floor | Distribution, zoning, stack effect, floor-specific envelope exposure | One random window gasket as the only explanation |
| Beside a window or exterior door | Local draft vs cold-surface discomfort | Bigger furnace as the first answer |
| Basement / lower level / cold floors | Foundation/rim-joist exposure, cold surfaces, distribution | Thermostat reading alone |
| House feels normal but the bill is high | Usage, weather, billing period, rates, equipment efficiency | Comfort diagnosis by itself |
A cold room is not proof of missing insulation. A cold whole house is not proof of an undersized furnace. These are routing clues, not diagnoses.
The furnace is running constantly - is that bad?
Not necessarily.
Long heating runs during the coldest weather can be normal if the home is maintaining the thermostat setpoint and the equipment is operating safely. Runtime alone is not enough to diagnose a bad or undersized furnace.
The more important distinction is:
It runs and maintains temperature
That can be normal during sustained cold. If the house still feels cold, shift attention to drafts, cold surfaces, humidity, and room-to-room distribution.
It runs but the indoor temperature keeps falling
That deserves a broader assessment.
Possible categories include:
- a heating-system performance problem
- a heat-distribution problem
- outdoor conditions beyond what the system is currently handling
- unusually high building heat loss from air leakage or insulation/envelope weaknesses
Symptoms alone cannot tell you how many BTUs the home needs or what R-value is missing.
If the furnace itself is not starting, use Furnace not working. If the blower is moving unexpectedly cold air, use Furnace blowing cold air. If it repeatedly starts and stops, use Furnace short cycling.
Heat pump? Judge the room, not your hand at the vent
Heat pumps commonly deliver a larger volume of air at a lower temperature than a gas furnace. NRCan explicitly contrasts this with furnace heat. If a heat pump is running steadily and maintaining setpoint, supply air that feels less hot than furnace air is not automatically a fault.
The furnace-blowing-cold-air guide explains that distinction in more detail.
Why is one room colder than the rest of the house?
If the rest of the home reaches setpoint, the heating plant is clearly capable of making heat. The next question is whether that room is receiving and retaining it.
Check the simple things first:
One cold room: safe first checks
- Confirm the room supply register is open and not blocked by furniture, rugs, or belongings.
- Confirm the return grille or normal return-air path is not obstructed.
- Compare airflow with nearby rooms without dismantling ductwork.
- Notice whether closing the room door makes comfort or airflow noticeably worse.
- Look at the room itself: corner exposure, exterior-wall area, large windows, a floor over an unheated garage, attic exposure, or a long duct route can all change the diagnosis.
- Notice whether wind makes the room much colder; that points toward an envelope leakage investigation as well as distribution.
If airflow is obviously weak only at that room, or the room changes dramatically when the door is closed, a qualified HVAC balancing/distribution assessment can be more useful than adding a portable heater and forgetting the cause.
Why is the basement or lower floor so cold?
Lower levels combine several effects that can feel similar:
- colder foundation and slab surfaces
- air leakage at sill plates, rim/band joists, service penetrations, windows, and other lower-envelope joints
- less heat delivery or poorer mixing than upper floors
- winter stack effect, which tends to draw outdoor air into lower parts of the house while warm indoor air escapes higher up
NRCan describes winter stack effect as the house behaving like a chimney: air tends to enter at lower levels and leave at upper levels. See Keeping The Heat In: comprehensive air leakage control.
That does not mean every cold basement needs spray foam. First identify whether you have an air leak, a cold surface, a heat-distribution issue, or a moisture problem.
If cold air is concentrated along trim, baseboards, door/window joints, or accessible penetrations, use the draft diagnostic. If there is active seepage, dampness, staining, or mould, follow the water/moisture problem before covering it with insulation.
Why do windows feel drafty even when they are sealed?
Because moving air near a window is not always outdoor air.
Room air touching cold glass can cool and fall down the pane. Your ankles then feel moving cold air at the floor and it is easy to assume the sash is leaking.
Before replacing the window:
- close and lock it normally
- use a tissue or thin strip of plastic at the moving sash and fixed trim joints
- look for actual movement at a specific joint
- if there is no movement, treat the cold glass and frame as a surface-temperature problem rather than proof of leakage
NRCan’s retrofit guidance treats air leakage and window heat transfer as different mechanisms. That is why the weather stripping guide tells you to diagnose the joint before choosing a seal.
Air leakage: where should you look first?
NRCan calls air leakage control the single most important retrofit activity to consider first in a home upgrade strategy. Its current guide lists common leakage locations throughout the house, including:
- doors and windows
- attic hatches
- ceiling light/electrical penetrations
- plumbing and duct penetrations
- joints between framing and masonry
- foundation wall and slab cracks
- sill/header and rim-joist areas
- fireplace/chimney interfaces
- service penetrations
See NRCan’s comprehensive air-leakage guide.
That is also why whole-house comfort problems should not be reduced to “replace the windows.” The biggest leakage path can be nowhere near the place where you feel the strongest draft.
A safe homeowner leak check
On a cold or windy day:
- close exterior doors and windows normally
- inspect visible seals and joints
- use a tissue or thin plastic strip to look for movement
- note which symptoms become worse with wind
- note lower-level versus upper-level patterns
- look for staining, frost, condensation, damaged seals, or obvious gaps
NRCan describes smoke-based leak detection too, but ReadyHome prefers the no-flame tissue/plastic approach as the easy first pass.
Do not create your own aggressive whole-house depressurization test around fuel-burning appliances. NRCan warns that house depressurization and insufficient combustion air can cause combustion products to spill indoors.
When is a blower-door test or EnerGuide evaluation worth considering?
Professional testing becomes more useful when:
- drafts are widespread rather than isolated to one obvious joint
- several rooms have different comfort problems and you cannot find a clear path
- you are planning a substantial air-sealing or insulation retrofit
- you want a measured pre/post airtightness result
- the heating system appears to operate normally but the house repeatedly loses heat or remains uncomfortable
- you want a whole-home energy evaluation rather than a single product recommendation
NRCan says professional air sealers and energy advisors can use a depressurizing fan door (blower door), smoke tools, and infrared scanning to find air leaks. An official EnerGuide home evaluation includes an airtightness measurement using a blower-door test plus assessment of insulation, windows/doors, heating, cooling, water heating, and ventilation equipment.
A blower door does not magically tell you which contractor to hire, and a single airtightness number does not tell you which individual crack is leaking. The value is controlled measurement plus a systematic way to locate and prioritize leakage.
For the testing details, use Blower Door Test in Canada: Cost, Results & Is It Worth It?. That page owns CFM50/ACH50, preparation, costs, thermal imaging, EnerGuide boundaries, and the decision about whether testing is worth paying for.
Is your house cold or is the heating bill just high?
Those are related problems, but they are not the same problem.
If comfort is normal and the bill suddenly jumps, start with the bill before diagnosing the building.
Compare these five things
- Consumption: compare kWh, cubic metres, or GJ rather than the dollar total alone.
- Billing days: a 34-day bill should not be compared casually with a 28-day bill.
- Actual vs estimated meter read: an actual read can include a correction after earlier estimates.
- Weather: colder periods require more heating energy even when nothing is wrong with the house.
- Rates and fixed charges: the price of each unit and non-consumption charges can change independently of household efficiency.
Environment and Climate Change Canada defines heating degree-days as the number of degrees a day’s mean temperature falls below a base of 18 C, with zero heating degree-days when the mean is 18 C or warmer. It is a useful weather context for comparing heating demand. See the ECCC climate glossary.
You do not need to build a spreadsheet before calling anyone. The practical idea is simply to avoid comparing January dollars with December dollars while ignoring weather, days, and consumption.
When a high bill deserves more investigation
Look harder when physical energy use rises substantially even after you account for colder weather and billing-period differences, especially if the home also has a new comfort symptom or heating-system behaviour change.
Possible categories include:
- thermostat schedule or occupancy changes
- a heating-system issue
- auxiliary heat behaving differently on a heat-pump system
- new air leakage or building work
- insulation/envelope changes
- a newly conditioned space
- a meter/billing issue that the utility needs to explain
ReadyHome deliberately does not use a universal percentage threshold such as “15% more energy per degree-day means your house is broken.” That kind of cutoff depends too heavily on the home, equipment, occupancy, weather, and data quality.
Can low humidity make the house feel colder?
It can contribute to comfort, but humidity is easy to over-diagnose.
Health Canada’s general mould-prevention guidance supports a broad indoor RH range, while its colder-weather guidance is conditional on what the building envelope can tolerate without condensation. The practical winter target therefore changes with outdoor conditions and the house itself.
Use a hygrometer and the dedicated Canadian indoor humidity guide rather than increasing humidity because the room simply feels cold.
If windows are already wet or frosted, use the window-condensation guide before adding more moisture.
A 20-minute cold-house walkthrough
Use this order before spending money:
Cold-house walkthrough
- Safety: rule out CO alarm, suspected gas leak, smoke, fire, sparking, burning electrical smell, or water on electrical equipment.
- Scope: decide whether the problem is whole-house, one room, one floor, lower level, or beside one opening.
- Heating behaviour: note no-start, cold supply air, repeated short cycles, long steady operation, or indoor temperature falling despite operation.
- Air movement: use tissue or thin plastic at suspect joints; note whether wind makes the symptom much worse.
- Cold surfaces: compare comfort near windows, exterior walls, floors, and interior areas away from the envelope.
- Humidity: measure RH if dryness, condensation, or frost is part of the complaint.
- Bill: compare energy units, billing days, actual/estimated read, weather, and rates before calling a bill increase a heat-loss problem.
- Escalate: use the specific ReadyHome furnace/draft/humidity path or arrange professional HVAC / home-energy assessment when the problem remains broad or unclear.
What should you fix first?
There is no universal order for every cold home, but there is a sensible decision order:
Swipe across the table to compare all columns.
| If you find… | First path |
|---|---|
| Furnace will not run | Heating-system troubleshooting / qualified service |
| Furnace blows cold air | Cold-air heating diagnostic |
| Furnace repeatedly starts and stops | Short-cycling diagnostic |
| One cold room, rest of house normal | Distribution plus local envelope assessment |
| Confirmed localized door/window draft | Weather stripping / fixed-joint sealing as appropriate |
| Widespread drafts | Systematic air-leakage / energy assessment |
| Cold window with no detected leak | Surface-temperature / window-performance strategies |
| Window condensation or frost | Humidity + cold-surface diagnosis |
| Cold basement plus moisture | Water/moisture source first, then thermal work |
| High bill with normal comfort | Consumption, weather, billing, rates first |
Frequently asked questions
Why is my house so cold even with the heat on?
If the heating system is running, check whether it is actually maintaining indoor temperature. A house can still feel cold because of drafts, cold windows/walls/floors, poor room-to-room distribution, or low-level comfort issues even when the thermostat reaches setpoint. If indoor temperature keeps falling, assess both the heating system and whole-home heat loss.
Why is one room colder than the rest of the house?
That usually moves distribution and local envelope exposure higher on the list. Check the room supply register, return path, door effect, windows/exterior walls, floor/attic exposure, and whether wind changes the symptom. It does not automatically mean the furnace is too small.
Why are my floors so cold in winter?
Cold floors can reflect a cold slab/foundation, an unheated space below, rim-joist or lower-envelope air leakage, or simple surface-temperature differences. Check where the cold is strongest and whether actual air movement or moisture is present before choosing insulation or sealing work.
Is a furnace supposed to run constantly when it is very cold?
Long runs can be normal during severe weather if the home maintains setpoint and the equipment is operating safely. Runtime alone is not a sizing diagnosis. A system that cannot maintain temperature, repeatedly faults, blows unexpectedly cold air, or short cycles needs a different path.
How can I find where my house is losing heat?
Start with symptoms: whole-house vs local, wind sensitivity, cold surfaces, visible gaps, and actual air movement. NRCan recommends systematic air-leak detection and says professionals may use blower-door testing with smoke tools and infrared scanning. For widespread or confusing problems, controlled testing is more useful than guessing from one cold spot.
Why did my heating bill go up so much?
Compare energy consumption, billing days, actual/estimated meter status, weather, and rates before assuming the building changed. If weather-adjusted physical use appears to be rising and the house also has a new comfort or equipment symptom, investigate the heating system and envelope.
Methodology
How ReadyHome built this guide: We used the supplied Canadian research dossier as a discovery and synthesis document, then narrowed high-risk claims against current federal sources. The routing logic intentionally avoids symptom-based estimates of ACH50, furnace capacity, insulation R-value, percentage heat loss, or guaranteed repair savings. NRCan supports the importance of air leakage control, winter stack effect, and professional blower-door/infrared diagnostics; Health Canada owns the CO safety gate and humidity/condensation context; Environment and Climate Change Canada provides the heating-degree-day definition.
Primary sources used
- Natural Resources Canada - Keeping The Heat In: how your house works
- Natural Resources Canada - Comprehensive air leakage control
- Natural Resources Canada - Operating your house
- Natural Resources Canada - EnerGuide home evaluations
- Health Canada - Preventing carbon monoxide exposure
- Environment and Climate Change Canada - Climate glossary
Sources & further reading
Check the original guidance for details that apply to your home. How we use sources
- Health Canada
Preventing carbon monoxide exposure
Generator placement, CO exposure, and fuel-burning appliance warnings.