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Retrofitting for passive heating | DoItYourself.com

Since homeowners seem to find cheaper and more environmentally sustainable ways to regulate the temperature of their home, passive heating becomes very popular. Passive houses are designed with the building envelope in mind, and how best to contain or keep out warm and cool air. This article takes a look at the different ways that the average homeowner and DIYer can retrofit their home with passive heating.

What is passive heating?

Essentially, passive heating uses the sun's exposure as best as possible and keeps the heat in and out as needed. For all passive heating systems to work, the first step is to measure where your home is in relation to the sun and take advantage of the solar hours. The angle of the sun shifts as the seasons change, which most people will be well aware of when dealing with extreme temperature changes.

Ideally, smart passive warming will consider how the sun is lower in the sky during the winter months and higher in the summer. Passive solar heating systems take seasonal changes, solar angle, hours of sunlight and temperature into consideration when designing the best retrofits. Systems will vary depending on climate and location.

 window wall with bright sun coming through trees

Solar power

Solar energy is an important part of properly designed passive heating systems. By capturing sunlight through properly positioned windows, using thermal mass and other passive heating structures and systems, there are many ways to use one of the earth's greatest sources of heat: the sun. When sunlight enters the home through windows, the area heats up. This heat is then dissipated as the sun sets and the temperature drops. Specific structures called "thermal pulp" can be used to store this heat and spread around the home. Concrete, bricks and containers of water are examples of thermal mass and will slowly release the heat they capture back into space.

Trombe Wall

A Trombe wall is a popular design that uses "thermal mass" and sunlight. This type of wall made of brick, concrete or other masonry is built so that it is south facing and either painted a dark color or with dark materials to best absorb sunlight. It is then completely covered by windows or glass, separated by only a few inches in between. When sunlight penetrates through the glass, the Trombe wall sinks into the radiant heat where it is stored and is slowly released through ventilation openings in the space behind it.

The heat is gradually dissipated, which means that most heat the home towards the evening as the sun goes down. The heat is prevented from leaking outside the glass and the air space in between. When you do it correctly, a Trombe wall can reduce your home's energy consumption by about 30 percent.

Thermal Sifhons

Sunlight can also heat water very quickly and thermal siphons benefit from this. These solar heating systems are usually quite simple to design and do not need much material. A tank holding water must be installed above a "collector" which then transfers heat to the house. These tanks should be protected or insulated at cooler temperatures so that there is no risk of freezing or blasting.

 Solar water heater mounted on a roof

Thicker walls [19659003] For homes that experience cooler temperatures, investments in thicker walls around the home can save thousands a year in heating costs to more layers of insulation (either foam, cellulose or bats) and cover them with properly sealed materials that won t let the heat escape. Most homes do not have the extra square pictures for this to happen on the inside (you need at least a foot) but an easy way to add layers to the outside of the home. This method also helps to cool your home in times of extreme heat.


Windows is a primary feature of passive solar heating because they are the main way sunlight enters and heats a home. South facing windows can be added to a home's space so that they are in direct view of the sun and its angle and utilize as much heat as possible. If it is not possible to add windows due to budget or other problems, existing windows can be replaced and updated to triple varieties that are installed, sealed and fitted correctly for reduced air leakage.

 windows with sun coming from a snowy winter forest

Many newer environmentally adapted windows will also reduce glare and overheating, or if there are specific areas in the home that are prone to overheat, these windows can be toned. Other solutions to control glare use shades, thermal curtains and blinds. On the back, there are all great solutions to keep cold air out when the sun goes down.

Building Envelope

Smart passive heating design will take the "building envelope" more seriously than basic construction, which usually makes passing barely codes. Taking the time to plan was windows, shaded areas, trees, roof lines, sunlight and other space elements is one of the best ways to use passive heating in the most natural way. Sealing the building envelope, where air transfers in and out of your home, will then help contain the natural heat that the sun rays in, and will also keep cool air in as needed. Focusing on materials and design with the building envelope in mind will directly affect how much money is spent on heating and cooling your home.

Most American homes will benefit from retrofitting solar heating, as 60 percent receive enough sunlight to make costs profitable. Most passive heating systems will be more advantageous for homes in climates that experience major temperature changes between day and night and summer and winter. Many aspects that help heat your home will also help cool it, and most are common sense and a matter of good planning. Not every retrofit will benefit every home, but every home will benefit from some form of passive heating retrofit – it's just a matter of figuring out which one is right for you.

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