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Comfort Specialist, HVAC Technician
Category: HVAC
Satisfied Customers: 1368
Experience:  Master Lic. holder for HVAC & Gas, Contractor, Estimator, Designer, Air Balance Certified, LG Master Commissioner, UNC Cert. holder for Industrial Ventilation
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# After coating a large commercial roof and ducts with a heat

### Resolved Question:

After coating a large commercial roof and ducts with a heat reflective coating the return air temp is now 3 degree C cooler on average (23 degree C day)
Comments from Air Conditioner service provider.
They noticed a marked difference in running time of the main shopping centre unit.
Their comments were that the Air Conditioner units would always be running whenever the ambient temperature was above 21C.
Now it gets up to around 28C before they kick in.
How do I calculate the energy saving
Submitted: 5 years ago.
Category: HVAC
Expert:  Comfort Specialist replied 5 years ago.

Wvfan79 :

Hello there! I'm Norman but you can call me Norm. Let's see what I can do to get you some answers today. I'm ready to get started whenever you are.

Wvfan79 :

A general rule of thumb is that energy savings can be 2% to 4% for every 1 degree difference in thermostat set-point; either raising the cooling setpoint or lowering the heating set-point. That would be for a 24 hour period.

Wvfan79 :

To estimate the savings from set-points during unoccupied periods; prorate the percentage based on the number of hours of set-back / set-up.

Wvfan79 :

Here's an example, if you are raising the cooling temp by 10 degrees for a 12 -hour period, estimated savings can be between 10% and 20%.

Wvfan79 :

That can be calculated like: 2% to 4% per degree * 10 degrees * (12 hours/24 hours) = 10% to 20% savings

Wvfan79 :

However, these estimates are just percentages of your electrical specifically used for heating and cooling. This is not a percentage of your total electric bill.

Wvfan79 :

Also, actual savings will depend on your specific climate zone. Savings as a percentage of your heating and cooling bill will be greater in mild climates than in higher/harsher climates.

Wvfan79 :

Wvfan79 :

If you have more questions and you reply to this post it may take me awhile to respond. I will try to check back once in awhile but glitches in the chat system do not allow for notifications of chat replies.

Wvfan79 :

Customer:

Hi Norm I am sorry for the no reply . the setting on my work pc did no show your data.