How to Make a Basement Warmer in 9 Steps

Increase Your Livable Space This Winter

Insulation and Remodeling
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Project Overview
  • Working Time: 2 days
  • Total Time: 2 days
  • Skill Level: Intermediate
  • Estimated Cost: $300 to $5,000 or more

Make a basement warmer in winter with long-term solutions that tackle cold air at the source. A major drawback to basement living is that this space can be cold, drafty, and not very inviting to anyone seeking a cozy indoor space. A basement that can be cool on a hot summer day can be chilly when the weather is cold. In many homes, a basement that is otherwise nicely finished still remains largely unused unless it can be made warm enough.

Yet basements are the logical place to expand additional living space. Considerable effort and money go into making basements warmer and less drafty, but all too often, these standard solutions don't entirely fix the problem. If your basement is freezing during the colder months of the year, it's important to insulate the right places. Fortunately, there are several easy ways to increase the heat in your basement.

Standard Solutions

Basements need active heating. Commonly recommended solutions are the insulation of the below-grade walls and floors or the addition of heating. Radiant-heat floors are often too costly and electric radiant-heat floors cost over $12 per sq. ft. to install. They will also increase your utility bills significantly. Hydronic systems will cost less to operate but installation will be very expensive.

Extending your home's existing HVAC ductwork system to the cold basement areas is usually the best solution. It can be expensive but is more affordable than other alternatives, provided your furnace has enough capacity to handle the extra heating load. You can also insulate the walls and floors by adding studs, filling the cavities with insulation, and finishing off with drywall or paneling. For floors, install sleeper strips, add insulation, and lay a new subfloor and flooring on top.

Limitations of Standard Insulation Methods

Although insulating walls has a striking impact on reducing heat loss in upstairs walls, it doesn't seem to have the same effect on below-grade walls. This is because the earth itself regulates basement temperatures effectively.

In the modern residential basement, the primary source of cold is usually not heat loss through the below-grade walls and floor. Instead, address your attention up high—at the short section of the foundation walls that lie exposed above the earth, and overhead to the rooms and framed walls that are above-grade.

Better Solutions

If your basement already has finished walls and ceilings, insulating them may not be cost-effective. The energy savings will not overtake the cost of improvements. Instead, consider other strategies to reduce heat loss and draftiness in your basement.

In most cases, your basement is cold because of air drafts and heat loss up high—at or above ground level. Ground-level cold is the real culprit. It cascades into your basement through windows, ducts, vents, pipes, spaces around intrusions, around the rim joist, header joist, and from non-conditioned rooms overhead. Warm up a cold basement by fixing the sources of cold air, which addresses the coldest entry points into the space—all without ripping out floors or walls. Insulating the right parts of your basement is the best long-term solution to make your house warmer.

What You'll Need

Equipment / Tools

  • Thermal camera

Materials

  • Extruded foam Insulation
  • Fiberglass batt insulation
  • Spray foam sealant
  • Insulated ductwork (where needed)
  • Energy-saving vent flaps

Instructions

How to Make a Basement Warmer

Systematically inspect and evaluate the various areas of your home as directed below, and make whatever repairs are indicated. You may only find some of the steps relevant to your situation.

  1. Locate Cold Spots With a Thermal Camera

    View the interior with a thermal image camera or thermal detector. If you are finishing your basement, this step is a must. Thermal imaging cameras are no longer just for house inspectors and energy auditors. Cheap but effective cameras can be purchased for a modest investment. Leasing a camera from an equipment center is also an option.

    Locate the cold spots: Stand in the center of a room and view the various areas through the viewfinder to pinpoint where your energy losses are occurring.

    Tip

    Fall and winter are the best times to finish your basement, at least from an energy-control standpoint. This is the time when temperature spikes are at their greatest and will be more visible on the thermal camera.

  2. Insulate the Rim Joists and Headers

    Add insulation to rim joists and headers. The non-insulated rim joists and headers of your house are the biggest contributors to heat loss. These framing members of the floor platform rest on the concrete foundation and cause significant heat loss. In older homes, these spaces are often left uninsulated. Insulating these is essential to making the space warmer.

    • Cut pieces of 1 1/2-inch-thick extruded foam insulation.
    • Insert them into the joist spaces against the outer rim joists and headers
    • Seal the gaps around the foam with a spray foam sealant such as Great Stuff.

    Alternately, pieces of fiberglass batt insulation can be loosely rolled up and stuffed into the joist cavities against the header.

  3. Insulate the Ducts Leaving the Basement

    Remedy these unimpeded "freeways" that shoot cold air straight into your basement. Dryer and bathroom fan ducts are little more than tubes of thin aluminum or paper-thin plastic, and they provide zero insulation from the cold. 

    Fix this with one of the following methods:

    • Replace these ducts with inexpensive insulated ducts
    • Wrap your existing metal ducts with insulation.
  4. Install Better Vent Flaps

    Replace cheap, ineffective vent flaps with an energy-saving "floating shuttle" type of vent flap.

    Most vents (the flap-like fitting where the duct leaves the house) are terrible at preventing cold air from migrating into your house. Little more than a thin plastic door, these vents let cold air pour into the duct, and thus into your house.

  5. Insulate Above-Grade Basement Walls

    Improve basement walls that are not protected by earth—such as those found in walk-out basements—in one of the following ways:

  6. Make Sure First-Story Walls Are Insulated

    Remember your basic science: cold air descends. If the walls on the first story above the basement are not insulated, they can act as conduits for cold air to move down towards the basement. Insulating an entire level's worth of walls just to cure basement cold is probably not cost-efficient, though it might well pay off when you consider the overall energy costs and comfort of your home. But if you are looking to identify where cold air is entering your basement, remember that the cause may not be in the basement at all.

  7. Confine Utilities in an Unheated Space

    Erect insulated interior walls that block off functional services, such as a furnace, water heater, and washer and dryer, preserving heat for the basement areas that are usually inhabited. Confine the furnace, water heater, washer, and dryer in a single unheated room. This will make it easier to control the temperature in other parts of the basement.

    Make sure to allow for the necessary ventilation space when enclosing utilities. Some high-efficiency furnaces draw their combustion air from the room space surrounding the furnace, and it's important not to impede this air source.

  8. Insulate Basement Ceilings Below Unheated Spaces

    Add insulation to basement ceilings below unheated areas. Rooms on the ground level that are not heated will compromise your efforts to heat the basement below. Some homes may have basement spaces below unheated porches or garages making it just as necessary to insulate the ceilings to hold in the heat. This will prevent it from migrating to the unheated space above.

  9. Add Heat

    Supplement basement heating as they lack the benefit of solar heat gain. However, adding heat sources alone is wasteful. Practical measures to block drafts and prevent heat loss are necessary. Luckily, there are some economical means of adding heat to a basement.

    • Modify the existing HVAC system. Contact a contractor to do this work during the remodeling phase rather than after to save cost.
    • Install modest electric baseboard heating units.
    • Place portable heaters around the space.

    It is important to make sure that the heat-loss solutions described above have been followed before adding supplemental heat.

Quick Tips for Heating Basements

After upgrading your home's insulation and addressing chilly drafts, there are a few additional solutions to cold basements that can increase the temperature:

  • Add carpeting or area rugs to hard flooring.
  • Turn ceiling fans clockwise in winter to circulate warm air.
  • Keep HVAC vents open to maintain a more consistent temperature throughout your house and decrease the load on your equipment.
  • Use caulk to seal the edges of windows.
  • Consider replacing older windows and doors with energy-efficient upgrades.
  • Add thermal curtains to decrease heat loss.
  • Purchase an electric fireplace or space heater.
  • Install a fireplace or wood pellet stove to save on energy costs.
FAQ
  • What temperature should a basement be in winter?

    Most basements stay between 55 and 60 degrees Fahrenheit throughout most of the year. If your living space is extended to the basement, you can increase the temperature by upgrading your insulation in areas where heat loss takes place.

  • What is the most efficient way to heat a basement?

    Once you've addressed cold spots by sealing and insulating, you can increase the temperature by adding baseboard heaters or radiant floor heat.

  • What is the cheapest way to heat an unfinished basement?

    The most inexpensive solution is probably portable space heaters. Electric heaters are easy to buy and do not need professional installation. All you have to do is plug it in and let it blow hot hair. It will work quickly to warm up the immediate space around it.

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  1. Ventilation Requirements. Energy Code.