February 18

Sealing & insulating for energy efficiency

If you put together all the cracks and leaks in a typical Canadian home, you would end up with a hole in the wall the size of a window. Warm air escapes from a suprising number of places throughout the house. Here’s how it usually breaks down:

  • Basement sill plates 25%
  • Exterior electrical outlets 20% 
  • Windows 13%
  • Pipe and wire entrances 13%
  • Vents 10%
  • Baseboards, light fixtures, electrical outlets, attic hatches 7% Exterior doors 6%
  • Fireplaces 6%

Fortunately, it’s easy to patch these leaks. Caulking and weatherstripping is the easiest, most inexpensive do-it-yourself task you can undertake, and it can cut your fuel bill by as much as 20 per cent. And because it tends to comprise a series of little jobs, you can do a little bit at a time.

Finding leaks may take some detective work. Check to see if your doors and windows fit tightly, and see if exhaust fans and vents close properly and are sealed around the edges. To find leaks, try this simple test: get two sticks of incense. On a windy day, hold the two sticks together and light them so you can clearly see the smoke. Hold them near areas where there may be air leaks. A strong leak will dissipate the smoke and cause the tips of the incense to glow brightly. Slower leaks will blow the smoke in one direction or draw it towards itself.

Remember to check plumbing pipes, vents, and fans that may let cold into the kitchen, bathroom or laundry room. Use butyl rubber or latex caulking.

Before you begin to caulk windows, check for rot, mold, the condition of the glass, putty and paint. You might just want to replace them. If not, at least clean them up before you begin caulking.

If you are adding insulation to your house, caulking and weatherstripping should be done first. Otherwise you’ll be putting insulation over leaky walls.

Check behind your baseboards. Many houses have open gaps that can be sealed with caulking.


There is a lot to think about when buying caulking: will it be used indoors, outdoors or both? Also think about the color, whether you can paint over it, what surfaces it will adhere to, what size gap it will seal, what temperature is required for application, what preparation is required and how long it will last. There are many different types of caulking which are suited to specific jobs.

SILICONE: is suitable for indoor and outdoor jobs and is mildew and moisture resistant. It’s available in clear form and is therefore good for applications where you don’t want to see the caulking.

ACRYLIC/ ACRYLIC LATEX: can be solvent-based for outdoor jobs or water-based for indoors. It’s paintable and adheres to most surfaces.

BUTYL RUBBER: good for indoors, it has good adhesion on metal, concrete and other masonry surfaces. Ventilationis required during application and curing.

ACOUSTICAL SEALANT: good for sealing polyethylene air-vapour retarders, but should be used only where it is sandwiched between two materials. It bonds to most surfaces, especially metal, concrete and gypsum board. It is not paintable.

URETHANE FOAM CAULKING: available in spray cans, it’s good for wide openings and hard-to-reach places.

OIL OR RESIN-BASED CAULKING: not recommended because it dries out, may stain wood and have a short life span.


Weatherstripping is used around doors and opening parts of windows. When choosing among the many types of weatherstripping, consider the size of the gap to be sealed, the durability, appearance and ease of installation. To be effective, it has to close off the gap completely without interfering with the operation of the door or window.


  • Adhesive-backed foam, available in rolls
  • Inexpensive, yet least durable
  • For use along the bottom of vertical sliding windows, hinged windows, doors and along attic hatches.


  • a more durable alternative to foam strips
  • works well on irregular surfaces


  • hollow or core filled, made of rubber or plastic
  • must be fitted carefully to ensure strong closing pressure for a good seal
  • attaches with nails, staples, or screws
  • used for doors or swinging windows


  • “V”-shaped vinyl strips can be used instead of foam, rubber or tubular gaskets
  • adhesive backed, easy-to-install, good durability
  • available in small or large “V” format
  • for use along the bottom of vertical windows, sliding joints of double hung windows and doors


  • similar to vinyl but generally used just for doors
  • installed using tacks


  • spring-loaded mechanism
  • adjusts to unequal distances from weatherstrip to door or window
  • installed using screws


  • system uses a magnetic strip and a metal strip
  • effective for doors and hinged windows
  • Sealing doors


  • a vinyl or rubber sweep screwed to door bottom
  • do not use where door must clear high carpet


  • vinyl or rubber strip attached to door thershold
  • provides an excellent seal but subject to traffic and weathering


  • attachment strip that fits over the bottom of the door
  • needs minimum clearance of 8 mm to 13 mm (1/3 to 1/2 inch) under door


INSULATING SWITCHPLATES: foam gaskets for electrical outlets and switches are easy to install, inexpensive and very effective.

EXPLORE THE ATTIC: Hot air rises. That means it heads for the attic, and from there it exits through leaks and cracks, accounting for somewhere between 10 and 15 per cent of warm air loss. First, caulk the attic floor to prevent moisture from escaping to the attic – this easiest in winter, because you’ll probably be able to feel the spots where warm air is entering from below. Caulk around light fixtures, interior wall partitions, plumbing and electrical lines, chimneys, flues, bathroom fans and the attic hatch. A butyl rubber caulking is recommended. Then you are ready to insulate. Two words of caution: do not put insulation material near the chimney; never step between the joists – the ceiling won’t support your weight.

LEAKY BASEMENTS: The gap between the basement or foundation wall and the house wall – known as the sill plate – lets out 25 per cent of the average home’s warm air. The gaps should be filled with butyl rubber, urethane foam caulking or an acoustical sealant. For larger openings, use polyurethane foam. Any cracks in the foundation walls or slab should be patched with an appropriate material such as cement.

INSULATE PIPES: A couple of rolls of inexpensive pipe wrap are all you need to insulate hot water pipes. This helps reduce the energy lost when hot water starts to cool before it reaches its destination. As a minimum, you should insulate the first one to two meters (three to six feet) of hot water pipe from your water heater. Hot water will arrive at the faucet at higher temperatures more quickly.

INSULATE WATER HEATER: wrap your electric water heater with an insulating blanket to prevent hot water from losing its heat to the surrounding air.

FIREPLACES: a fireplace is not the best way to add warmth to your living room. A roaring fire may give off a cosy glow, but your chimney is actually a major cause of heat loss and drafts. When not in use, always close the damper as soon as the fire is completely out. Fireplace doors will also save energy. Also check where the chimney meets the wall and the floor. It could probably use some caulking.


Now that you have caulked, weatherstripped and insulated your home to lock in the warm air, it might be necessary to address the question of air quality. A well sealed house can often retain excess humidity, causing condensation on windows, mirrors and walls. In extreme cases, you will notice peeling paint, mildewed walls, water stains and musty odours. Ordinary activities like washing and drying clothes, cooking, bathing, even breathing, can add as much as 23 litres of water to the air every day. An air tight house will also retain stale air, lingering odours (cooking, painting) and second-hand smoke.

Your house may also need extra air supply if a fuel-burning furnace is operating at the same time as other major air-exhaust systems (including fireplaces, powerful exhaust vents or open windows on upper floors). This combination of circumstances can starve your furnace for air and impair its operation.

Opening a window may solve ventilation problems temporarily, but ultimately, it severely reduces the energy efficiencyof a home. The problem with a “leaky” house is that escaping air collects in the walls or attic, where it condenses and causes rotting. Cold outside air rushes inside, and it must continually be heated. Furthermore, the distribution of the fresh air throughout the house is completely uncontrolled and you will have lost any advantage you gained by caulking, weatherstripping, window replacement, etc. Air sealing saves the house structure, improves energy and improves comfort.

A heat recovery ventilator will solve the problem by giving you control over air quality and humidity levels. It automatically controls ventilation, delivering a steady supply of fresh air while creating a draft-free environment. Basically, the heat exchange is a box with two air streams: one supplying air to the house and one exhausting air from the house. The continuous supply of fresh outside air is made economical through the use of the HRV heat exchanger – while the air throughout the house is changing, most of the heat from the warm exhaust air is being transferred to the cooler incoming air.

The system also provides humidity control and eliminates the need for noisy bathroom and kitchen fans.

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Posted February 18, 2014 by Stiverrom49 in category Home Improvements

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