What is the Meaning of Passive Design?

Passive design is becoming more popular over time. Despite the fact that it was once standard practice, during the last 50 years it has been neglected and almost forgotten. With its new raise, some people are not aware of what it is and of its history and tradition.

So, what is the meaning of passive design? Passive design maximizes the natural light, heat, and air movement in a specific location in order to create a comfortable interior environment that reduces the need for energy to light, warm, and cool a building.

Now that we know what is the exact meaning of passive design, let’s have a look at how is it achieved and what principles are involved.

How is Passive Design Achieved?

The following four points are the main topics that are tackled to achieve a passive design. They are as follows:

  1. Natural ventilation
  2. Building orientation
  3. Natural lighting
  4. Insulation

1. Natural Ventilation

Natural ventilation is very effective in climates where the air outside has a comfortable ambient temperature for many months in the year. Hoverer, this passive design strategy is not very common in climates with fewer days out of the calendar year in which a building can be occupied without being mechanically heated or mechanically cooled.

When you are using natural ventilation as a strategy for passive design, you need to consider the way air moves around the space.  There are a few factors that you must keep in mind, such as the window’s orientation. Consider all the openings that are intended for natural ventilation and the way air moves. For instance, you should know that hot air rises and cold air sinks.

The balance between passive and active systems is achievable by relying on passive systems before getting to the active system’s set point. This setpoint can be reached by using natural ventilation systems with the windows open. This way, the rooms will remain cool, and the active system will not kick in.

Natural ventilation has so many enjoyable benefits. It meets industry standards for air quality and ventilation for buildings of all uses and the need for condensation prevention. Natural ventilation allows fresh air into interiors, thereby ensuring that buildings designed for commercial and domestic properties are healthy, safe, and you can comfortably work and live in them.

Passive design homes replace stale air in your home with fresh air from the outdoors, making it possible to regulate humidity and internal temperatures. Fresh air is just as essential as allowing enough natural daylight into your interiors, and passive design does it all for you.

In order to achieve good natural ventilation, cross ventilation is a common strategy. In this strategy, a house or building has opening in opposite orientations and, by opening both at the same time, the air will flow. There are other strategies such as using an atrium or double spaces that can also help with that.

2. Building Orientation

For a good passive design, you need to consider your budget, program, microclimate, and site specifics. The way the building is orientated plays a major role in passive design. However, most energy-efficient designs face the north or south for better solar energy management.

One of the simplest and very effective passive design strategies is orientating the building to harness the heat from the sun. The building is orientated in such a way that it follows the movement of the sun. This orientation is very beneficial since the same heat that comes in through your windows during winter can ruin your comfort in the summer.

Exterior shades, overhangs, and deciduous trees can be used to keep the summer sun out. Also, thermal mass, such as a concrete wall or floor in the building, can be used to store winter heat. The building is designed to be elongated with a narrow building footprint to allow more daylight. When it comes to massing, this is the best form of passive design.

Your building can be designed to have a single or multi-story, but it has to be lengthy, north, or south-facing for excellent passive design. Facing the longest façades north and south enables the building to take advantage of indirect sunlight from the north. The building is also able to gain controlled direct solar heat from the south.

Direct heat gain from the sun at the east and west-facing glazing are reduced using exterior shading during the period when the building is mechanically cooled. In the summer, exterior horizontal shading elements are used to control direct heat gain from the sun at the south-facing glazing. The sun is at its peak during this period. The building can also take advantage of direct heat gain from the sun during winter when the sun is lowest.

3. Natural lighting

Daylight is another factor involved in passive design. The climate of the region in which your building is located determines the kind of windows you need. In hot climates, the building keeps heat out with windows that have low-E coatings to exclude radiant heat. These windows can also lower solar heat gain coefficients.  

On the other hand, cold and mixed climates are a bit more difficult, sometimes it is hot, and other times it is cold. And this can make a few faces of the building to either gain or lose heat. Generally, in colder climates, windows should be designed so that it takes into account the wall they sit in. Exterior shading is very important when positioning windows and glazing.

It is not usually easy controlling direct heat gain from the sun, but it maximizes daylighting from the north. It does this by orientating skylights for best-quality daylighting. Applying strategies for daylighting is also useful for south-facing glazing. It can also help for east and west-facing glazing.

The importance of using advanced technologies and window systems cannot be overemphasized. Cutting-edge glazing and coatings have also been found to be very useful. It is crucial to know the impact of heat gain, natural light, and glare on building systems design. Engineers downsize building systems by coordinating the windows’ location, the massing of the building, and daylight harvesting using mechanical and electrical design.

By doing this, they can match the high-efficiency goals of the project. They use louvers and grilles to protect the openings on the building envelope from debris while letting air in and out of the building. Solar heat gain during warm periods can be reduced using louvers and grilles as exterior shading elements.

Exterior shading can be fixed or operable and are used to block the unwanted sun from streaming into the living space in the summer. They also allow heat in during winter. These exterior shades and grilles are made in a way that follows the sun’s path for that specific location.

4. Insulation

Including insulation in a building is another excellent passive design strategy. Usually, there are only a few requirements by energy code when it comes to insulation. A good passive design strategy would be to design the building envelope above the code requirements by adding more insulation. If you have your building is designed properly by including electrical and mechanical systems and a passive design structure, you will save cost.

And this is because the additional money used for better windows, better insulation, and a better roof mean that you will not have to spend money on frequent maintenance. Insulation is essential for buildings in cold regions. It enables the building envelope to resist the conductive flow of heat. Insulation works best when it is installed continuously, and this lowers thermal bridging more than cavity insulation.

Continuous insulation is when the building is wrapped up on the outside, using a blanket of insulation. And this thermally separates the inside from the outside, and there are no thermal bridges. It is not only beneficial for comfort and energy performance, but also indoor mold elimination and air quality. Thermal bridges usually become cold spots, which can condense moisture out of the air inside your home, just the way a glass of lemonade does. These cold spots are usually unexposed corners in which rot can develop, mold can grow, and bugs can come in without you noticing.

Passive design buildings also use light shelves, curtain walls, a slim building design, and an east-west orientation to bring daylight to about 95 percent of interior spaces. This also reduces the need for lighting during the day because most of the rooms can harness the light from the sun.

Introduction to Passive Design Principles

Now that we have seen the four main topics, it is time to look at the principles that are used to achieve a good passive design. Some of them have already been mentioned above, but we will elaborate on them in this section.

A good passive design that is well-suited for your climate has a lot of benefits. Passive design is very important because it provides low heating and cooling bills. You get to experience thermal comfort and a huge decrease in greenhouse gas emissions. What this means is an extended life span of your home.

This design is achievable by, as we said, properly orientating your building and carefully designing your home’s walls, roof, floors, and windows. Designing these building envelopes right will help you reduce unwanted heat loss and gain.

The best time to achieve an excellent passive design is when your home is still under the design stage. During this period, you will get to spend the lowest possible amount of money required for a good passive design. However, renovating an existing home for this purpose can also be cost-effective. Your thermal comfort could get a lot better, even with small upgrades. If you are getting a new apartment or home, ensure that you assess its thermal comfort prospects.

Besides, it is also important to know if you can cost-effectively upgrade it for excellent passive design. For you to get the best results, you need to be an active user. You need to understand how passive design home works with the climate.  You need to know the right time to open or close your windows. And the basic knowledge of how to operate adjustable shading is also required.

Let’s have a look now at the main principles used for passive buildings.

Building Science Principles behind Passive Building

The passive design approach uses five building science principles that give you unmatched comfort, predictable performance, great air quality, and resiliency in the face of power outages due to winter storms or summer blackouts.

1. Continuous insulation can break thermal bridges between inside and out

When a building is completely wrapped with insulation, it is able to retain heat. No thermal bridges mean that the heat cannot find a route where to escape through. It also means that cold spots will not be present and, as a result, the appearance of mold will be much less likely.

The most common places where thermal bridges appear are in the slabs, and especially in the balconies. Careful detailing from your architect or relevant responsible person is required in order to avoid these. Certain roof areas can also be prone to thermal bridging if the detailing is not properly done. 

2. A super tight building only needs minimal mechanical

Since the building is well-insulated, tight with high-efficiency windows, the need for cooling and heating systems is reduced. Part of the money you spent on windows and insulation can be regained using smaller mechanical systems.

In mild climates, you will not even need cooling and heating. Thanks to the insulation, your building will stay at a comfortable temperature all year around.

3. Balanced ventilation gives room for fresh air and controls moisture

Passive design comes with a lot of air tightening, meaning that moist or dirty air cannot leak into your living space. However, a good ventilation strategy is critical in this case.

In the past, because of the low quality of the windows, the air circulated always, so you would get the ventilation through the gaps within the window. Currently, and especially with high-quality windows, the air will not flow unless you design a system for that.

Apart from opening the windows to take care of the breezes to cool down the building, the air circulation needs to be controlled with some type of high-tech fan. You can use, for example, an ERV (energy recovery ventilator) to pull in new air and push out the old air. This ventilator also allows you to transfer moisture and heat in the process.

4. Airtight construction is used to stop heat

Building upon the previous point, in summer, an airtight construction impedes the warm air from getting into the building. Also in this case is a good ventilation strategy critical.

With a good ventilation design, you can make sure that you get enough fresh air circulating while at the same time making sure that the air that goes in does not warm up the space.

5. Optimized windows are used heat in and out

Apart from double glazing using argon gas – a typical design strategy of Energy Star windows, passive buildings have most times triple glazing. They use low-E coatings on the surface of the glass and fine-tuned it in such a way that it allows less or more heat gain. Also, high solar heat gain windows can be used on sides of the building where winter sun is required – usually on the south and east sides. 

Passive design houses also involve the use of low SHGC windows. These windows are required in places where the summer sun can cause the most harm – usually the west side.

Passive Building Standard

The Passive House Institute US Inc. (PHIUS) is a Chicago-based nonprofit organization. They aim at setting high-performance passive building as the mainstream market standard.

The PHIUS+2015 Passive Building Standard is the only one that focused on performance and climate-specific comfort criteria. It is also the only standard that demands on-site QA/QC for certification. PHIUS+2015 has its main target on the sweet spot between investment and payback. It presents a cost-efficient solution to help you get the most affordable and comfortable house on the market. It offers an excellent way of achieving zero energy and carbon.

According to PHIUS, houses designed and constructed to the PHIUS+2015 standard have a 60 to 85 percent higher performance. However, this depends on building type and climate zone when it comes to energy consumption as opposed to a code-compliant structure following the International Energy Conservation Code (IECC 2009).  A moisture and energy modeling tool is used to dial the strategy into a particular climate, WUFI Passive.

This tool can create a hygrothermal model that shows you how your house will perform at several periods of the day and year. It also accounts for the actual site, including any billboards or shade trees that could block the sun. Passive building is based on a number of building blocks – the same as LEED, Energy Star, and the Department of Energy’s Zero Energy Ready Home designation.  

Passive building certification ensures that you get a net-zero building that is durable, provides more comfort, and has many health benefits. There are currently more than one million square feet of PHIUS+ Pre-Certified and Certified projects across one thousand and two hundred units nationwide.

The PHIUS+2015 has been standard updated with the PHIUS+2018, and this will eventually become the standard. If you are interested in learning more information about the PHIUS+ Passive Building Standard, you can access this website.

What Are The Benefits of Passive Design Homes?

Passive design building is a useful method of construction that improves your life. It has a lot of benefits, and I have listed them below. They include:

1. They provide great comfort

As I mentioned earlier, one of the benefits of a good passive design is comfort. This design enables you to make the climate inside your house exactly as you desire. And you get to do this without any cooling or heating systems. This means that even when the weather is too hot or too cold outside, you will still be very comfortable in your house.

2. High quality

Passive design homes come with a high level of airtight design and insulation, which is one reason for the numerous praises showered on them. Also, passive houses use the “thermal bridge free design,” which enables the insulation to be applied without weak spots on the entire building.

What this principle aims to achieve is the elimination of cold corners. It also gets rid of excessive heat losses that may occur.

3. Passive homes are energy efficient

Passive houses are designed in such a way that enables them to be highly energy efficient. Passive homes are capable of using about 90 percent less energy than the current building stock. Even though they consume less energy, they perform the same functions as traditional houses. And sometimes, they can even perform way better.

Basically, with the way passive homes are designed, fuel bills will be lower due to reduced energy consumption. And this will be very beneficial to you since you can save money while helping to reduce greenhouse emissions.

4. They are ecologically friendly

When you look at the meaning of passive design houses, you will see that passive homes are eco-friendly. The energy that they use comes from the sun, so they only use little primary energy. One thing about using only little primary energy is that it leaves enough energy resources for our future generations and also it does not cause any harm to our environment. 

Therefore, this means that building a passive home is an effective way of helping to protect the environment. It helps limit the emission of greenhouse gases, thereby preventing some respiratory diseases and climate change. 

5. Passive home design is affordable

In the long run, passive houses will definitely save you money, but aside from that, they are actually affordable in the first place. It is a surprising fact, but it is a fact all the same.

The investment in higher quality building components needed by the Passive House Standard is lowered by getting rid of costly cooling and heating systems. Also, some countries provide additional financial support, thus making it more feasible to build passive houses.

6. Versatility is key in passive design

Passive House Standard is well-suited for every type of buildings and any climate zone. This means that any architect on the market that knows what they are doing can easily design a passive building. However, due to the versatility of this type of building design, the application of the Passive House Standard is now beyond the residential houses. 

Some time ago, only residential buildings applied this standard. However, in recent times other types of buildings are starting to use it too. Many factories, office buildings, schools, and even swimming pools have integrated the Passive House Standard in their structural design. With this, one can undoubtedly say that this standard does not impose any limitations on materials or construction methods. This means that the Passive House Standard is very versatile.

Final thoughts

A good design for a home must be comfortable and ecological. However, a passive design home possesses these qualities and is also energy-efficient and affordable. Buildings with this design enable you to regulate your home’s temperature without having to pay any cooling or heating bills.

While choosing a design for your home, remember that with passive design, you have one that saves you a lot of money.

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