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How to Calculate Heat Loss in a House?

Heating contractors often want to run a home energy audit before deciding what type of installations and developments should take place on your property. 

This is where a trained professional conducts home heat loss calculations to determine how much heat is escaping from your room.  

Knowing the results of the heat loss equation will allow you and your contractor to choose a heating system, such as radiant flooring to effectively and efficiently heat the room of your choosing. Here’s how to calculate heat loss in a house.


Key Notes

  • Heat loss measures the amount of heat energy transferred to the outside of a building through a surface or material.
  • Calculating heat loss helps determine the energy required to keep a room at a desired temperature on the coldest possible day.
  • To calculate heat loss, identify the design temperature, determine surface area, and calculate R and U values.

What is Heat Loss?

what is heat loss

Heat loss is a calculation that measures the amount of heat energy that is transferred to the outside of a building through a surface or material. 

Most commonly, experts focus on calculating heat loss through a wall. A heat loss calculation will typically be measured in either BTUs or kW. 

The heat loss through walls calculation identifies how much energy is required to keep a room or space at a desired temperature on the coldest day. 

It is essential to know what heat loss is and how to calculate it through a wall, as this will tell you what type of heating system you need to efficiently heat your room to a comfortable temperature.

How to Measure Heat Loss in a House

how to measure heat loss

As mentioned, there are several steps that you, your contractor or your energy auditor need to take to calculate heat loss through your walls and ducts. 

6-step method to measure heat loss in your home:

1. Identify The Design Temperature of Your Home

The design temperature differs between your preferred indoor temperature and your local area’s average coldest possible temperature. 

The design temperature, a straightforward calculation, is measured as Delta T.

2. Determine The Surface Area Of The Room That You Intend To Heat

When calculating heat loss through a wall, you will want to calculate the surface area by using the total length of an exterior wall and the height of that same wall. 

Eliminate the size of any windows or doors along that wall when calculating the room’s surface area. 

To complete the calculation, you will want to configure the surface area of doors and windows separately.

3. Calculate Both The R-Value And U-Value Of Your Room

The R-value and U-value of the room help you to calculate heat loss through the wall while keeping in mind the impact that insulation has on the room. 

A room with insulation in the wall will have a higher R-value than one without adequate insulation. 

You must first calculate your R-value, and then you can use that number to determine the U-value of the room.

4. Determine The Surface Heat Loss

The surface heat loss identifies how much heat is lost through a wall due to doors and windows along the exterior wall. 

The surface heat loss can be calculated by determining the U-value of the doors and windows along that wall. 

Their U-values can be part of the heat loss equation to determine your total heat loss through a wall.

5. Calculate The Amount Of Air Infiltration Heat Loss

Air infiltration heat loss is a separate figure that will identify the amount of heat that is being lost through small cracks, joints and caulk around the windows and doors on an exterior wall. 

Air infiltration heat loss may seem minor and insignificant, but it can significantly impact the total heat loss in a given room. 

However, air infiltration heat loss can be fluid, as a room’s wind speed and temperature changes impact it. 

A specific formula can be used to determine air infiltration heat loss.

6. Use A Heat Loss Formula To Determine Total Heat Loss

Here’s the formula for calculating heat loss through a wall:

Total Heat Loss = (Surface Area) x (Delta T) x (U-Value) + (Air Infiltration Heat Loss)


Surface Area = the total surface area of the exterior walls (excluding windows and doors) in square feet

Delta T = the difference between the design temperature and the outdoor temperature in degrees Fahrenheit

U-Value = the overall heat transfer coefficient of the wall in BTU/(hr·ft²·°F)

Air Infiltration Heat Loss = the amount of heat lost due to small cracks, joints, and caulk around the windows and doors in the wall in BTU/hr

Once you have determined all of the various figures and calculations that are included as part of the heat loss equation, you can identify what the total heat loss is within your room.

The Impact of Heat Loss

Heat losses and heat transfers will play a significant role in the effectiveness of your heating solution. It is essential to understand the impact of heat loss when you are investing in a new heating system, such as underfloor heating, because the amount of heat loss will determine whether that solution will be effective or not. 

These are just a few of the reasons why you should identify where heat loss is occurring and determine the U value rate of a given space before you invest in an underfloor heating system for your home:

  • The amount of heat loss that takes place in space will ultimately determine what type of equipment is needed in order to adequately heat the area. 
  • The heat losses in a room could have an impact on the regulatory approval of the space.
  • In a space with significant heat loss, you and your contractor may have to come up with innovative solutions to properly heat the space and keep everyone who will use the space as comfortable as possible.
  • The heat loss calculation will also help you and your contractor determine how much energy will be required to heat the space, and it also can help you predict future heating costs.

On the surface, heat loss may seem like a minor measurement that can easily be overlooked, but it plays a pivotal role in the long-term success of your heating system.

Frequently Asked Questions:

What is The Average Heat Loss in a House?

Generally, a well-insulated and sealed home may experience heat loss ranging from 1% to 5% per hour. For example, if the indoor temperature is 20°C (68°F) and the outside temperature is 0°C (32°F), the heat loss would be approximately 0.6°C (1.08°F) per hour. 

We recommend a professional consultation for a more accurate and specific reading for your home or property. Want To Calculate The Heat Loss of Your Home Accurately? Contact Green Wave Distribution Today.

How Much Heat is Lost Through The Floor?

While calculating heat loss through walls is essential, it’s also crucial to consider the amount of heat lost through the floor. Heat loss through the foundation can account for up to 10% of the total heat loss in a room.

To calculate heat loss through the floor, you need to know the flooring type and the insulation thickness beneath it. Additionally, the calculation must account for any air gaps between the floor and the insulation layer.

Using Home Heat Loss Calculations to Choose the Best Radiant Floors For Your Home

At Green Wave Distribution, we work closely with our clients to determine the best home radiant floor solution. 

Our radiant flooring heating mats stand apart from the competition mainly because of their innovative features, which include:

  • Self-regulating carbon polymer heating technology. This thin, flexible and durable technology prevents the system from overheating.
  • Low-voltage powered technology, which also improves the safety of the entire system.
  • Even heat distribution. Our flooring system will heat your room quickly and evenly and prevent heat loss from occurring. 
  • Environmentally-friendly materials. All system components are designed with recycled material and are landfill biodegradable.

Why GreenWave Distribution?

At GreenWave Distribution, we understand the importance of maintaining a comfortable and energy-efficient living space. 

To learn more about our radiant heat solutions and how they can help you reduce your energy costs, contact GreenWave Distribution today or explore our other heating products.