A furnace that is not producing adequate heat is not only wasting your energy, but it's also making you live in an uncomfortable place. This is why you should know why your furnace may malfunction in such a way; it may help you find a solution for the issue. Here are some of the common causes of inadequate heating:

Low-Temperature Setting

The thermostat controls most of your heating system's functions; it makes sense that the thermostat should be your first port of call if the furnace isn't heating your house to the desired temperatures. If you are lucky, you may find that the issue is as simple as a thermostat that is set too low. In that case, simply turning up the temperature setting to the desired level should solve your problems.

Air Flow Blockage

In some cases, it might be that the furnace is working and producing the level of heat it should be producing, but the heated air isn't being circulated properly. This may be the case if something is blocking the airflow. For example, physical objects in the ducts such as insulation that has fallen off, accumulated debris, and insects can obstruct the ducts and reduce air flow. Clearing the obstructions should get your furnace heating optimally again. Other possible causes of airflow problems include dirty air filters, blocked heating registers, and closed zone dampers, among others.

Malfunctioning Blower

The blower is responsible for forcing the heated air through a system of ducts that ensure the air reaches all the target rooms. This means your house will not be heated if the blower is malfunctioning since the heated air will not be reaching its destination. This may be the case, for example, if the blower fan is damaged and cannot handle an optimal volume of air.

Air Leaks

It may also be that the furnace is just producing the level of heat is it meant to produce, but the air is leaking outside your house as soon as it is produced. This may be the case, for example, if the air ducts have cracked in their joints or the attic isn't properly insulated. Plugging the air leaks should help.

Improper Sizing 

Lastly, your furnace may also fail to heat up your house to desired levels if it is too small for the area you want it to heat up. Maybe the furnace was properly sized during installation, but you have since remodeled your house and added some rooms that also need to be heated. In this case, you may have no option but to upgrade the heating system.