Why do I have rooms in my home with different temperatures?

Whether you are using a forced air furnace or a hot water boiler to heat your home, temperatures may vary from room to room. Each room in your home will lose heat to the outdoors thru the windows, walls, floor and roof. Since some rooms have more windows or a greater area of exterior wall, each room will lose heat at a different rate. Therefore, the duct providing the warm air or the radiators that disperse heat from the hot water must be specifically designed for the heat loss of that particular room. What we find mostly is that the furnace or boiler has the capacity to replace all of the heat being lost from your home, but the distribution system (ductwork  or boiler piping/radiators) is either incorrectly balanced or undersized. We will discuss solutions to these two problems.


  • Forced Air: Forced air systems that use duct to deliver warm air throughout your home require an air balance based on specific heat loss calculations that will determine the correct volume of air that should be delivered to a room. Air volume is measured in cubic feet per minute  (CFM) and a proper air balance will ensure that the correct volume of air is delivered  to each space. Balancing is achieved by adjusting a damper to either increase or decrease the volume of air. If a damper is 100% open but the volume required is not present at that register, the volume may still be boosted by cutting back air flow to rooms that may have excess air flow. Every time a damper is adjusted,it effects the air flow to all of the other registers attached to that duct system;so a balance project  requires the air balancer to continuously  re-measure the air flow after each adjustment. Sometimes the duct can be so restrictive (incorrectly sized) that the optimal quantity of air cannot be delivered from your furnaces blower. If this is the case and your total volume is within 10% of optimal design,the balancer will balance all rooms within  that percentage. However, if the deficiency is greater than 10%, additional duct will be required to prevent  any damage occurring to your furnace.
  • Hot Water: Boilers heat water and deliver this hot water to the radiators using a pipe system and require a balance to ensure the proper volume of water is being delivered to each radiator. A heat loss calculation as above will determine the exact volume of hot water needed to be delivered to a room. Water volume is measured in gallons per minute (GPM) and a proper balance will ensure that the correct volume is delivered to each radiator by actually measuring the water flow thru each radiator. Typically, radiators have balancing valves at the outlet  side,these are call circuit setters and by adjusting the circuit setter, the balancer can vary the volume of hot water thru that radiator. As above, changing the volume to one radiator  will impact the volume at the other radiators so the balancer must continuously re-measure the water flow after each adjustment.


Whether you are using forced air or hot water, if the distribution system is undersized it will be unable to deliver the required  heat.

  • Forced Air: A forced air furnace utilizes a series of air ducts to deliver the conditioned  air to each space. There are two main ducts, one for supply air and the other is for return air;both are equally important. If either the return  duct or the supply duct are undersized, your blower will only deliver the quantity  of air that can be carried thru the most restrictive duct. Duct that is undersized for a particular room is something that can usually be easily addressed by adding an additional branch duct to that space. However, if the main duct is undersized, this will typically require replacement of the undersized duct to ensure all branch leads off the main duct have sufficient volume of air to properly condition the spaces
  • Hot Water: The boiler will use a series of pipes to distribute the hot water to each radiator  and like forced air,there are two main pipes that carry the hot water,one being the hot water supply and the other the hot water return;again, each being equally important. Two factors can contribute to a room being left under conditioned. First, if the pipe delivering hot water to the radiator  is undersized, it will not provide enough hot water to allow the radiator  to heat the space;this is typically not the case. Most times it is the radiator that is undersized for the space whereas there is not enough length to the radiator to replace the heat that the space requires. Possible solutions are to replace the radiator  with one that has a greater capacity or add an additional radiator to the space. Some people may feel that increasing the water temperature will provide the solution to their problem  but you should be very careful as increasing water temperature will only satisfy the thermostat faster and may actually cause the space that was not heating correctly  to feel less comfortable.The first step then when addressing a room that is under conditioned is to perform a heat loss calculation to determine if the distribution system is adequate. The residents of Oswego, Ill. have come to trust the approach that RJ Kuhn takes when trouble shooting these areas as their professional recommendations always resolve the issues. Often,the solution  can be quite a simple fix,others may be more complex; it just depends on how much access the construction of your home allows us