When the temperature drops in our homes, what is the first thing we do?
Turn up the heat, of course!
But let’s face it, as nice as a good heater feels, running it non-stop is expensive.
So, what if there was a way to naturally heat your home?
Oh, well, there is!
Passive solar heating is as old of a concept as the dawn of Earth.
All you need is a bit of sunlight and heat-absorbing building materials, and–voilà–you have yourself a passive solar-heated home!
If it’s so simple, why don’t we use it more?
That’s a great question.
In this article, we’re going to take a look at everything you need to know about passive solar heating.
If you’re getting ready to build a new home, you may want to think about implementing this energy-efficient, money-saving concept!
1. What is Passive Solar Heating?
Passive solar heating uses the energy from the sun to store heat in a home’s materials.
That’s the basic gist, but successfully designing such a system is a more complicated task.
Here’s what a home needs for passive solar heating to work:
Thermal mass (bricks, stone, tiles)
Temperature control strategies (roof overhangs, shades, vents)
Typically, for this system to work, the home needs to have south-facing windows, within 30 degrees of true south, that do not get shaded by trees or other buildings from 9:00am to 3:00pm during the heating season.
Next, a home needs to have building materials that can absorb enough heat.
The most common materials used in passive solar-heated homes are brick, stone, and tile.
These materials should be in an area that the sunlight from the south-facing windows can reach.
The stored heat is then distributed through conduction, convection, and solar radiation.
Conduction is the transfer of heat between two objects, such as your feet being heated by a warm floor.
Convection is the transfer of heat within a fluid, such as air or water (hot air rises, cold air sinks).
Radiation is the transfer of heat through electromagnetic waves, which is the reason you can feel the warmth emanating from a heat lamp on your skin.
Controlling passive solar heat is a bit trickier than adjusting a thermostat.
You need to use overhangs or blinds to block the sunlight during hot days.
In addition, you could also use fans, vents, blinds, shutters, and awnings.
That’s the big idea of passive solar heating; pretty ingenious, right?
Let’s now take a closer look at a few different passive solar heating methods that are important to consider when building a home.
2. What Are the Main Types of Passive Solar Heating?
There are four main approaches to passive solar heating. Let’s take a look at each one and see how it works.
Sun-tempering uses south-facing windows to introduce heat to the living spaces inside of the home, helping to control the temperature.
This method doesn’t depend on building materials to store and release it; it simply uses the sun’s energy to bring warmth to a room.
Direct gain is the most common form of passive solar heating.
Sun enters through south-facing windows and heats thermal mass, such as brick, stone, and tile, to store and distribute heat.
Homeowners who use this method have to be mindful of the amount of sunlight coming in to prevent furniture from fading (too many windows can also make it difficult for a home to retain heat in the winter).
Indirect gain (also referred to as Trombe wall) is achieved by using a south-facing wall built with heavy masonry or sometimes containers of water.
The wall absorbs the heat from the day and slowly transfers it into the house as it cools.
The process is slower than direct gain but still an efficient method.
Isolated Gain (Sunspaces)
Isolated gain (also referred to as sunspaces) uses an area in a home that collects heat from sunlight and can be closed off from the rest of the building.
During the day, the doors or windows connecting the room to the house are opened so that the heat can warm the home.
At night, as the room cools, the doors or windows are closed so that it doesn’t affect the house’s temperature.
3. Is Passive Solar Heating Efficient?
Despite its simple concept, passive solar heating is very efficient.
Who would have guessed designing a home to work with the natural environment would make it energy efficient?
The best and most efficient part is that it is a passive heating system, as the name suggests.
That means there’s no work or energy required to obtain it, resulting in an efficient system that’s beneficial for the environment.
Homes that use passive solar heating systems typically use 25% less energy than a home that doesn’t–that’s a big difference!
4. What Are the Advantages of Passive Solar Heating?
There are a lot of benefits to using passive solar heating.
Anything that operates on a renewable source of energy, in this case, solar energy, is going to be less intrusive to the environment and less expensive to run.
Here’s a list of all the advantages of passive solar heating.
1. Saves Money on Electricity
Using the energy of the sun will decrease how often you use the heater to keep your house warm.
Passive solar heating can cut your energy bill by 25%, keeping money in your pocket.
Not relying on electricity also means your home will stay warm even if there’s a power outage.
2. Reduces Noise Pollution
Traditional heating systems require loud furnaces, pumps, and other equipment, causing noise pollution.
Well, passive solar heating is as silent as it gets.
It requires zero equipment that could cause noise (other than fans to help distribute heat).
Next time you run your heater or air conditioner, take note of just how noisy they really are.
3. Doesn’t Use Expensive Equipment
Once a house is designed to utilize a passive solar heating system, that’s it!
You don’t need to pay for any special equipment because, well, the sun is free!
Of course, there will be the upfront cost of the solar passive design and building (or modifying) the house to work with the sun, but after that, nothing else needs to be purchased.
4. Doesn’t Require Maintenance
Passive solar heating is a maintenance-free system–mostly.
Traditional heating systems frequently need to be worked on and replaced.
Well, with passive solar heating, unless there are structural integrity problems with windows, walls, and flooring, upkeep isn’t required–further saving you money.
5. Benefits the Environment
Traditional heating systems require a lot of electricity, and that electricity typically comes from fossil fuels.
But using solar energy to heat a home will reduce your carbon footprint because the system doesn’t require any sort of fuel to operate–minimizing pollution in the environment.
5. What Are the Disadvantages of Passive Solar Heating?
Despite all the benefits of passive solar heating, there are a few drawbacks. So, let’s check them out.
1. The Design Has to Be Just Right
Designing a home to utilize passive solar heating requires more thought than just putting up a few windows.
Every feature of the system, including windows, sunspaces, and materials used to absorb heat, needs to be balanced out perfectly.
Too much or too little of something can throw off the whole thing.
Anyone interested in using passive solar heating should work with a professional building company that knows how to design an efficient system.
2. Location Dependent
Different environments require different systems.
A passive solar heating system in California might not work as well as in Michigan.
Failing to do proper research on what system works best for the area could prevent the process from working properly.
3. Sun Exposure Issues
Passive solar heating usually requires sunlight to enter a room.
Too much sunlight can cause furniture to fade and damage plants.
Homeowners have to be very mindful of the areas of the house that get direct sunlight and plan accordingly.
4. Start-Up Costs
If you’re building a new home, implementing a passive solar heating system shouldn’t exponentially increase the building costs.
However, if you want to convert a home that’s already been built, that can get expensive.
Knocking down walls, purchasing materials, and all the other construction costs can add up quickly.
The good news is that once everything is set up, it should pay for itself.
6. Does Passive Solar Heating Work in the Winter?
Passive solar heating sounds great, but can it actually keep a house warm during the cold winter months?
It sure can!
In fact, winter is when passive solar heating really comes in handy.
During the colder months, the sun still shines, creating an opportunity to use its energy to heat a house.
Sure, there will be times it’s bitterly cold and the sun is nowhere to be found.
For those days, traditional heating systems are lifesavers, but passive solar heating is still an excellent alternative throughout the winter season.
7. Can You Have Too Many Windows?
Installing too many south-facing windows can result in heating problems.
In the world of passive solar heating, there’s something referred to as the 7% Rule.
The 7% Rule: If the surface area of the south-facing windows is 7% of the total surface area of the house, no additional thermal mass is required (homeowners wouldn’t have to add more brick, stone, or tile to the house).
However, if the surface area of the south-facing windows is greater than 7%, then extra thermal mass needs to be added.
If it’s not, it can cause the house to overheat.
Homes that use the Direct Gain system (see above section for more information) typically have south-facing windows that equal 12% of the total surface area of the house.
To monitor all the sunlight that comes in, these homes will typically have large brick/stone walls, large areas of dark tile, and other heat-absorbing tactics.
So, if you’re installing south-facing windows, carefully measure the surface area to find out if you need to add more thermal mass.
8. What Is the Best Flooring?
The flooring you choose for passive solar heating matters.
Choose the wrong material, and the whole system comes crashing down.
The best flooring options to use for passive solar heating are stone, brick, or porcelain and ceramic tiles.
You could use any of these options and see great results.
It gives homeowners a lot of options to find an aesthetic that they like.
The worst flooring options to use for passive solar heating are wood, vinyl, or linoleum.
These materials are poor absorbers and could prevent a home from being properly heated.
9. What’s the Difference Between Passive and Active Solar Heating?
While reading this article, have you been wondering if there’s something called active solar heating?
Well, there is!
But what’s the difference?
Passive solar energy systems are designed to obtain heat directly from the sun.
Active solar energy systems use the sun to heat air or water or to generate electricity, which is then used to heat a home.
Here are some examples of active solar heating systems.
Solar water heaters.
Active solar heating systems are typically more expensive than passive solar heating systems.
Additionally, these active systems are more intricate, which can lead to more problems.
Homeowners will need to do far more maintenance on active systems than passive systems.
However, both options will cut back electricity bills, reduce the burning of fossil fuels, and provide heat throughout the year.
But what type of system is better?
10. Is Passive Solar Heating Better Than Active?
Deciding whether passive or active solar heating is better than the other is a tricky task.
Active solar heating is the more efficient option, and some of the active systems can be relied on even without the sun.
If a house uses solar panels, it can store energy for a later time and power traditional heating sources, getting the best of both worlds.
Passive solar heating is always subject to the weather. No sun means no warmth.
But which one costs more?
In general, active solar heating is more expensive than passive solar heating.
An active solar water heating system could cost more than $10,000–not including the annual cost for regular maintenance.
The main cost for passive solar heating is window installation.
Homeowners can expect to pay $100 to $300 per window (the price can increase for more difficult installations).
But no matter what, both active and passive heating systems will pay for themselves over time!
It seems silly to not design our homes to use the energy of the sun, doesn’t it?
The good news is that implementing passive solar heating in your home can be as easy as installing a few windows and redoing your flooring.
In a matter of a few days, you could start saving money on electricity and doing your part in the fight against climate change.
But before you start knocking down walls and installing windows, talk to a solar heating professional to make sure your home is a good candidate!
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2 thoughts on “Passive Solar Heating: 10 Things (2023) You Need to Know”
I really doubt the benefits of passive solar heating. The basic theory says that in winter the sun will shine through my window and heat up the slab and tiles on the floor. This is then meant to store enough heat (thermal mass) to release heat during the night. Rubbish! Two main problems here. Firstly, sure in winter you might capture some of that heat in the slab but it dissipates at night very quickly and within 2 hours it’s equalised and your house is cold again. Then when summer comes around you have the same principle at work heating your home! The heat hits the floor, heats up your slab and you’re working doubly hard to cool the house down. I’ve never understood the theory of thermal mass and I think it sounds better in theory than in practice.
Hello Al, I can understand your skepticism. My understanding is that passive solar heating does work better in some climates than others and it certainly isn’t going to be as reliable as active heating. Still, I’ve read a number of case studies that do suggest it can work in the right location. I’d be curious to hear about your experience if you or someone you know has tried it!