If certain rooms in your house never seem to be warm enough, it's typically for one of two basic reasons: There isn't enough heat being delivered, or the room can't hold the heat.
If you've checked the insulation and it's fine, you might have a problem with your furnace ducts leaking and not supplying enough heat.
The ducts are hidden - in walls, under floors, running through attics and crawlspaces - so most homeowners never think of them. Leaking ducts can cause you to lose up to 20 per cent of your airflow - that's air you've paid to either heat or cool. It really adds up.
Put it this way: If they were water pipes and leaking, there's no question you'd be all over it. But leaking air? And the ducts could be leaking for years.
The leaks can be caused by lots of things: Bad connections and careless workmanship can make ducts literally come apart at the seams; insulated flexible ducting can tear on nails or become compressed, kinked or bent; nails driven carelessly though walls or floors can puncture it.
Leaks in forced-air duct systems are a major source of energy waste in homes.
Leaky ducts also let air into your heating, ventilation and air-conditioning system. And that air might contain dust and particulate matter, mould spores and pollen - all of which can affect your indoor air quality and family's health.
In addition, the leaks can cause "backdrafting" - meaning gases from combustion flow back into a home's living space rather than vent through the chimney. This is extremely dangerous, so it's very important to have your ducts checked for leaks, blockages and airflow.
If you find you've got a leak, the repair can be costly if you've got to tear out drywall and patch it.
The first step is fixing what you can see - the ductwork that's visible in an unfinished basement or attic space. Inspect it carefully, check connections in the ducts, as well as the heat registers and vents in your floors and walls.
You should check both the hot supply and the cold-air returns. Remember, your HVAC is a complete system and both processes need to be working well together.
If you find any broken connections or leaks, seal them. Use a metal tape that's designed for ductwork - not duct tape, which is great for lots of things - just not ducting.
If your ducting is run through an unheated part of your home - such as the attic or a crawlspace - you should insulate it. It will increase the energy efficiency of your home.
You can have an HVAC specialist come in and test your system to make sure it's working at optimum efficiency. In theory, if it's sealed and air tight, all the heat created by your furnace should be delivered equally throughout your house.
But sometimes that isn't the case because of leaks in the ducting. You need to test the airflow to determine why your system is out of balance and what you can do about it.
A blower is used to pressure test the system for air leaks, in much the same way a plumber tests water pipes for leaks. Air is forced through all holes and cracks in the ductwork and a precise leakage measurement is made using an airflow and pressure gauge. A fog machine can be used as well to show the location and extent of leakage.
Your HVAC contractor will also inspect the whole system; check your filters; repair any damaged, crushed or disconnected ducts; insulate and seal any ducts that need it - and most important - conduct a combustion safety test to make sure there is no backdrafting.
Mike Holmes is the host of Holmes on Homes on HGTV. For more information, go to www.holmesonhomes.com