There is a growing movement worldwide called The Passive House Movement. It began in Canada during the 1970’s and double-glazed windows are a key ingredient. A passive house is one in which energy is saved and thermal comfort is achieved with no mechanical means. Double-glazed windows reduce heat transferred into your home during summer, and heat escaping during winter, helping you to achieve thermal comfort.
Windows For Life supports the Passive House movement in Australia. All our windows help homeowners achieve high energy star ratings towards their passive home projects.
Read on to find out a little bit more about passive homes and how our windows can help you achieve a passive home, savings on your energy bills, and a peaceful and environmentally conscious way of life.
What is a Passive House
The Passive House idea began way back in Saskatchewan, Canada in 1977, and was revisited in Hanover, Germany, with a ‘zero energy’ house. This was then taken further with a house built by Dr Wolfgang Feist and Dr Bo Adamson, in Germany, 1991.
With people being conscious of energy prices and environmental concerns, the idea has bloomed worldwide. However, it is not just a case of building a home with some environmentally friendly additions. There are some strict conditions you must meet for your home to be considered a Certified Passive Home.
There is an official Australian Passivhaus Association website where you can find more information, and register your home to become a Passive House, and display the official plaque.
You are not allowed to display this unless you’ve achieved official certification as a Passive House.
Image: Passivhaus Institute
How Does A Passive House Work?
A Passive House is designed to maintain a comfortable level of habitation between 20 and 25 degrees C, mostly without mechanical means. They use features such as thermal insulation, reduced thermal bridges, being airtight, and more.
We say ‘mostly’ when it comes to mechanical means, as there can be some mechanisms involved with ventilation. Passive or natural ventilation can be inefficient, or require human intervention far too often. So some simple mechanical ventilation to assist with heat recovery is used.
Image: Passivhaus Institute
‘Passive House’ standards
There are standards and design principles that a house must adhere to if you want it to be certified as a Passive Home in Australia.
To be certified a Passive House, and earn the right to display the Passive House Institute plaque, your home must adhere to these 5 criteria:
- Indoor Temperature. It must be a maximum of only 20 degrees Celsius with no more than 10% of the hours in a given year over 25 degrees Celsius.
- Heating and Cooling. Heating demand must not exceed 15kWh/m2 per year or, the heating load cannot exceed 10W/m2. Cooling demand cannot exceed 15kWh.m2 per year and the load cannot exceed 10W/m2.
- Humidity. The humidity in your home must not exceed 12g/kg for more than 20% of the year.
- Airtightness. There must be a maximum of 0.6ACH50 (0.6 Air Changes per Hour, at 50 pascals pressure) with on-site verification.
- Energy Demand. Maximum primary energy renewables demand of 60kWh annually, per square metre of living space.
What Are Passive House Windows?
A passive house window is one that reduces heat loss from a house, and prevents heat transfer into the home through the window itself. It’s vital to find effective passive windows as they are essentially a hole in your insulated walls.
You want a window that denies most of the UV light streaming into your home and most of the warmth coming through the window as well. These same windows are needed to stop heat and warmth escaping through the glass.
Double-glazed windows, with a noble gas sandwiched between the panes of glass, are excellent passive house windows.
Image: Passivhaus Institute
How Much Money Do Passive Windows Save Me on My Energy Bills?
When researching double-glazed windows to help save on your energy bills, you need to consider the U Value. This is a measure of the window’s level of conductivity of heat and cold. The lower the U Value of a window, the better the performance, and the more energy you will save.
The noble gas between the panes of glass, and the use of non-conductive materials, such as uPVC, significantly lower the U Value of our windows.
Another factor which can impact the savings is the Solar Heat Gain Coefficient (SHGC). This is the amount of heat gained and then transmitted through the glass when it is exposed to direct sunlight. The higher the SGHC, the more heat is transmitted through the window. Northern facing windows in winter would have a higher SHGC than southward facing windows, for example. Allowing more heat in during winter is a very energy efficient way to warm your home, and save on energy bills.
Double-glazed windows alone can save you potentially $250 a year on your energy bills, and they are just one component of a full passive house.
Pros and Cons of Passive House Windows?
There are plenty of positives surrounding passive house windows, and we’d like to share them with you.
- Thermal Comfort. This is that feeling when you’re not too hot and not too cold, sitting on your couch, or in your bed, and the inside temperature is just right.
- No draughts. No sneaky cold air gusts from your windows in the cold of winter, and nowhere for the inside warm air to rush off to. It is a contributing factor to the air tightness of your home.
- Lower levels of Dust. With better sealing with passive windows, dust and irritants such as pollen, find it harder to get inside and bother you.
- Nice and quiet. Double-Glazed windows, with good sealing, stop a lot of outdoor noise pollution from intruding.
- Lower energy bills. As mentioned, you can save upwards of $250 a year on your energy bills.
There are some disadvantages with passive windows, of course, and in the spirit of fairness, we will present them to you.
- Higher upfront costs. It costs more to install passive windows, naturally. They are specially engineered windows, much more complex than single panes of glass. But, the savings you make down the track are absolutely worth it.
- Renovating and Extensions are difficult. Maintaining your passive home certification can be trickier and more expensive if you add an extension.
- More technical build. You need a builder who is aware of passive home requirements and can install your windows with precision to ensure airtightness and a reduced thermal bridge.
- You may not want to leave home as often. When you have a wonderful thermal comfort level, and reduced noise pollution, you may find staying home far more desirable than going outside.
The main difference between a passive house window and a standard window
A standard window is a single pane of glass in a frame. That frame can be wood or aluminium or other material. Light and heat can pass through very easily, so too UV radiation. The temperature differences in winter from outside to inside can cause condensation to form on the window. This can lead to moisture damage or mould growing in and around the window.
Passive windows, double-glazed windows, are two panes of glass, framed with uPVC, which is long lasting and an excellent insulator with a very low thermal bridge. There is Argon gas between the panes which is a terrible conductor of heat. This means in summer heat won’t get in, and in winter, your heat won’t escape through the window.
Passive windows also play a key role in reducing heat loss and raising the energy efficiency of your home, to help meet the standards of a Passive Home.
Definitions:
There are some technical terms used with passive windows. Below we have explained them for you to help you understand why passive windows are so good for your home.
- SHGC – Solar Heat Gain Coefficient, is the fraction of solar heat falling onto the glass that enters a room. If 600W of solar energy shone onto a pane of glass, and 200W entered the room, then the SHGC of that pane of glass would be- 200/600= 0.3. A small SHGC is preferred in summer, and a higher SHGC is a good thing in winter.
- U-Value – The U-Value is the measure of the rate of heat loss or heat gain through the window. The lower the U-value the better insulation the window has. To measure the U-value of a window you need to first understand the R-value, or resistance-value of all the elements that make up the window. The formula looks like this- U-Value = 1/(Sum of all R-Values).
- Low-E Glass – This stands for Low-Emissivity Glass, where emissivity is the amount of radiation emitted or absorbed by a surface, such as the window. Our double-glazed windows are Low-E windows, which means the UV radiation that strikes the window, very little of that is transmitted through the glass and into your home.
- Condensation resistance (CR) – It is a measurement of the potential formation of condensation on the inside of a window on a scale of 1 – 100. The higher the number the better. It is calculated by a weighted measure and summation of the positive temperature below the dew point temperature, with three points of relative humidity reference, at 30%, 50% and 70% humidity.
- Visible transmittance – With this, you’re referring to a fraction of the visible light spectrum that is transmitted through your window, or how well a window will light your room. It is expressed as a number between 0 and 1. A zero means no light is getting through whereas a value of 1 means all the light possible is getting through.
Passive homes are a big investment with big rewards. It is a positive and conscious effort to live in a way that is good for the environment and good for you in saving money on your energy bills. We are all for passive homes and saving you money through less energy on heating and cooling your homes.
Contact our team today to discuss Low-E Glass, Solar Heat Gain Coefficients, and other related topics.