These charts are for estimation purposes only and are not exact. Each house is different due to a variety of reasons including, but not limited to, location, type of construction, materials used and desired design temperature of the house. For proper sizing a whole house heat loss should be performed by a heating contractor.
If you are having problems keeping your house warm with your existing boiler, a larger replacement boiler may not solve the problem. Remember that you can only deliver as much heat as your radiation is capable of delivering. Inadequate heat can be symptomatic of other problems such as improper piping.
There are many factors to take into consideration when replacing your boiler. As important as proper sizing is to the system, it is just as important to evaluate your vent system to see if it needs to be replaced with the boiler or needs a new lining or to be resized.
Important reminder when replacing a steam boiler: you must size to the existing radiation and not to the heat loss of the house. The replacement steam boiler must be large enough to fill the radiation so that it will function properly.
