Uneven heat. It may be the No. 1 complaint among Arlington homeowners all winter, no matter how cold it is.

Many people who have multi-level homes, including town homes, apartments, and brownstones, deal with uneven heat at one time or another. The furnace is running, appears to be in fine order, but one room or floor is warmer than the other. Often noticeably so.

The mystery of uneven heat generates more calls to Arlington heating, ventilation, and air conditioning (HVAC) contractors than most other service and repair issues throughout the winter.

This post examines uneven heat. Why it happens. And what can be done about it. Before calling an Arlington heating repair contractor, examine what’s going on.

Common Causes

Are vents blocked or closed off? If there is a specific room that doesn’t seem to stay warm, the first thing you’ll want to do is check that all of the air vents are open and clear of obstructions. Sometimes homeowners close vents in rooms that are not used much and forget to open them when it’s used more frequently.

Look to see if a heavy piece of furniture is blocking a vent. Homeowners re-arrange the furniture in rooms and a piece of furniture may be blocking a vent, so the room may not be receiving enough conditioned air to keep it warm. Move the furniture if you can, or perhaps move it off the wall a bit to increase air flow.

Is the furnace filter dirty? Blame everything that goes wrong with an HVAC system on dirty air filters! It’s true. This is perhaps the best place to start sleuthing, according to 100 percent of HVAC service and repair techs and three out of four dentists. If the filter is clogged, it will restrict the amount of air that circulates in the home and some rooms may receive more warm air than others. An easy fix: replace the air filter.

Is it extraordinarily cold around windows and doors? Rooms with doors and windows that open to the outside are harder to keep warm than interior rooms. Cold air can leak through unseen openings and lower a room’s temperature without the homeowner being aware of a problem. Prevent this by sealing doors and windows with caulk and weatherstripping.

Ductwork

Poorly distributed heat may not be an equipment problem but an issue with ductwork. Start with a visual inspection of the ducts. Perhaps a box in the attic fell on a section of duct. Or a critter made a mess of it.

Leaking duct connections (images). Sections where ducts join can fail if they are not joined properly or the ductwork is super old. There are special tapes and joint materials that ensure a proper seal. If connections leak you’re losing heat and money.

Leaking return vents (images). Ductwork and vents should be sealed where they join. Return air can spill into the walls, the attic, or below the floor if there are loose connections. These are costly leaks.

Damaged or fallen insulation (images). Air traveling through an attic can rapidly lose temperature if ducts are uninsulated. All ducts installed in unheated areas should have secure insulation.

Damaged ductwork (images). Flexible ducting is used in attics and, because they are flexible, the ducts can be kinked or even collapse in sections, which chokes off airflow and reduces circulation.

Contact an Arlington HVAC Contractor

If you have not had an thorough HVAC inspection in a while and are experiencing uneven heat and/or air flow, chances are none of the above will make much sense. Call an Arlington heating and cooling contractor (or call several, the goal is to find one you trust) and schedule a service call. Ask if the technician is familiar with the issues you are having.

If the service or repair tech finds it’s a larger air flow issue, you may want to schedule an evaluation of the air distribution system where an “auditor” — someone trained in air balancing — will use a variety of diagnostic tests, including static pressure and blower door and duct blaster tests, to find the problem.

(Quick aside: This is a reason why it’s important to find an HVAC contractor in Arlington you trust. It will have talented and experienced service and repair techs on staff, and you will not have to look for another company to handle special assessments.)

Zoning System

Sometimes the shape and orientation of the home plays a role in how heat is distributed. While architects and builders have good intentions, sometimes they make decisions that result in negative implications far down the road.

For example, where is your thermostat located? It’s typically on the first floor, preferably in a well-trafficked and accessible location. The thermostat’s job is to read all the temperatures — downstairs and upstairs. When it gets warm enough (or cool enough in the summer) the thermostat shuts off the unit and may not pay attention to what the temperature is upstairs. As a result, it’s not warm enough upstairs. Or it’s too hot there and not warm enough downstairs.

One solution to this problem is using a “zoned system,” which divides your home into at least two heating/cooling areas so that the furnace and air conditioner heat and cool the “zones” at different temperatures.

This usually requires installing electronically controlled dampers in the ductwork. These dampers are like valves opening and closing to control the air flow of heated and cooled air throughout the home. If you have only one thermostat, a second will be installed so that each zone is controlled by individually.

Installing a zoned system is not inexpensive (perhaps $3,000, depending on the home’s circumstances and needs and contractor selected). Discuss this option with the company you previously selected in Arlington.

Ductless Split

Another possibility is adding a ductless split (images). It’s essentially and air conditioner without the ductwork. These small room-based units pass cold air through small air handlers mounted on the wall. The homeowner controls the temperature independently in each room the air handler is installed.

Costs for ductless air conditioners start about $1,500 per unit. Definitely call your Arlington HVAC contractor to see if this is even an option for you.

Wrong-size Furnace

You may have no idea about the HVAC equipment in your home, town home, brownstone, or two-story apartment. Most people do not. Sometimes furnaces (or entire systems) can be improperly sized. If the furnace is too small (or aged and not performing as well as it once was) it might not be powerful enough to provide adequate heat to every room. If the furnace is too big its heating cycles may be too short, which restricts its ability to heat the entire home evenly.

A second heating and cooling system may be needed, which can cost about $7,000 depending on many variables.

Other Suggestions

Some service and repair techs recommend closing the register in the room with the thermostat.

Others recommend leaving the fan in the “on” position. It keeps the temperature a little more even because air is continuously circulating throughout the home. It’s mixing all the air between the upstairs and downstairs. This approach concerns some homeowners who think running the fan continuously is a huge power draw and will add significant cost to the monthly bill.