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The Stack Effect

The air quality in your home can be affected by several issues. The stack effect is one of the least discussed yet most common issues in most Colorado homes.

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When you are trying to maintain good air quality in your home, there are many different factors you need to consider. From mold and mildew to humidity and even pest infestation, there are plenty of things that can lower the quality of air in your home. These issues, of course, are well understood, but the stack effect is less widely discussed and understood, partly because it has many different names. 

the stack effect

What is the Stack Effect? 

The stack effect is often called “the chimney effect” and refers to the way thermal differences impact airflow within a property. Part of this is to do with the natural movement of air, anyway. After all, warm air rises no matter where it is. 
Of course, a modern home is a somewhat unique space. Every building has a neutral pressure level (NPL) that represents its ideal state. When in this state, air movement into and out of the building is reduced, ensuring a more stable environment and ambient temperature in your home. When the stack effect starts to work on your home, however, this balance is disrupted because of entry and exit points at the top and bottom of your home.
Because of these access points, air from outside is continually drawn into and through your home. In winter, cold air from outside will be drawn into your crawl space as the warm air in your home rises and, eventually, exits your home. In summer, the effect can be reversed with the cool air from your HVAC system sinking and drawing down warm air from the outside. 

What Causes the Stack Effect? 

To put it simply, the stack or chimney effect is a result of entry and exit points that allow air to circulate from the bottom of your home to the top. This creates a draft throughout your home that can have a lot of side effects for you and your property. Of course, almost all properties will have an exit of some point for air, which means that when you notice the stack effect in your home, it is almost guaranteed that the issue is in your crawl space. 
Uncovered Crawl Space Vents 
If you have a non-encapsulated crawl space or unsealed crawl space vents, it is very likely that this is the cause of the stack effect at work in your home. Of course, there are other issues that can result from having an unsealed crawl space (some of which are arguably more pressing than the stack effect). From flooding to pest infestation and generally raised humidity, an unsealed crawl space is a real health and safety concern for your home. 
Thankfully, this is one of the most benign underlying causes of a stack effect at work. In fact, it can generally be solved with the addition of some high-quality vent covers. By having a professional install covers, you will not only cut off the main entry point for cold or humid air from the outside but protect your crawl space from flooding and reduce pests’ interest in the space. 
Floor and Wall Gaps  
If you have gaps forming between your walls and floors, you should call a professional to investigate immediately. This is because these gaps are a sign that the floor is beginning to fail as a result of a lack of support or damage to the floorboards themselves. As such, the stack effect at work in your home as a result of these gaps may not be your main concern. 
However, sudden changes in airflow and an increase in drafts around your home can be a good warning sign of structural issues like this. After all, airflow is likely to increase before gaps between your walls and flooring become too large. 
An uneven floor can also contribute to the impact of the stack effect within your home. This is likely to be less pronounced than it would be if the floor was pulling away from the walls, but it will have an impact because the spaces between floorboards are likely to change as they warp and bend. 
Structural Damage 
If you have sealed off your crawl space vents and your flooring is in good health, the most likely entry point for drafts in the lower reaches of your house will be areas that have sustained damage. If the sealant around entry points for vents, wiring, or pipes has started to wear away, for example, this will cause a mild form of the stack effect. 
Serious damage to your crawl space walls, however, is likely to cause a more severe and noticeable draft that has a pronounced effect upon your home. Dampness, bowing walls, and spreading cracks are just some of the other issues that this kind of damage could bring about. 

Health and Safety: The Effects on You and Your Home 

Some homeowners may think that the stack effect is not likely to have a huge impact on their homes or families. This is just not true, however. The presence of a stack or chimney effect in your home can have a huge impact on your health and well-being, as well as your home. 
The Impact on Your Home  
When the stack effect starts to go to work on your home, it is more of a symptom of damage than anything else. Nonetheless, it will cause certain issues to arise. 
Fire Safety 
Having increased airflow throughout your home has serious implications for fire safety. A channel that allows air to circulate from the bottom to the top of your home immediately will also allow fire to spread quickly throughout your property. This is concerning for obvious reasons and will have serious implications for your home and personal safety if a fire does break out. 
Temperature Fluctuations 
As air is drawn into and through your home, it will make it very hard to keep a consistent temperature for any length of time. This is inconvenient in the spring and summer, but in fall and winter, it can be very unpleasant. After all, the winters in Colorado can be incredibly harsh. In winter, a home that is struggling with the stack effect can become very cold. 
HVAC Deterioration 
As the airflow in your home increases and the temperature fluctuates, your HVAC system will have to work harder to get the same results. This will put it under strain and cause it to deteriorate at an accelerated rate. This will make your home’s HVAC system more prone to breakdowns and malfunctions and could result in you having to replace certain parts of the system earlier than you would have otherwise. 
Increased Energy Usage 
The fact that your HVAC system will have to work harder just to give you the same results (if not worse) means your energy consumption could rise quite drastically. This will cause a spike in your energy bills and cost you more money on a month-to-month basis. 
Mold and Mildew Spread 
If you have a gap somewhere in your crawl space, it is very likely that there is an increased level of humidity in that space. This will make it more prone to mold. If mold takes root in your crawl space, the spores will be carried through your home by the drafts caused by the stack effect. This will make them spread to other places in your home. There are many types of mold, and depending on the kind you have, this could have serious impacts on your property and your health. 

The Potential Impacts on Your Health 

Anything that impacts the climate of your home has the ability to also impact your health and well-being. Some are minor, of course, but there are others that are more alarming. This has much to do with whether you are in generally good health or have underlying health problems as well. 
Airborne Allergens 
As well as upsetting the balance in your home and causing temperature fluctuations, consistent airflow from outside can bring in allergens and dirt. If you have hay fever, for example, you will notice a sharp increase in the intensity of your symptoms when the stack effect is at work in your home. This is because the air being drawn in from outside of your home will be laden with pollen and other allergens. 
Respiratory Issues 
If you have mold and mildew in your home, or there are pests in your crawl space, the stack effect will cause airborne particles to circulate throughout. This can have a surprisingly serious effect on your respiratory system, especially if you have some of the more dangerous species of mold in your home. If you have underlying respiratory problems, this effect will be exacerbated and could lead to more severe ramifications that require medical intervention. 
Skin Irritation 
When this increased airflow causes particles of pollen, mold, mildew, dust, and dirt (among other things) to circulate in your home, there is an increased risk of you experiencing some kind of reaction. For those who have pre-existing skin conditions like eczema, the reactions can be quite severe. However, even if you don’t have any medical conditions, certain allergens are likely to cause issues, especially if you have an open wound. 

Frequently Asked Questions about the Stack Effect

While it can be tempting to view this as a relatively benign issue that will have no immediate impact on your home and health, we disagree. The stack effect is most commonly seen in homes that already have vulnerabilities or damage, but it can also have an impact of its own. 
The Stack Effect is a Symptom 
Even if you are not convinced that the stack effect is something to worry about on its own, you should be concerned as to how it is possible for it to take place within your home. While most properties have some kind of ventilation in the attic, the stack effect needs more than one entry/exit point. As such, the sudden onset of the stack effect should be a concern for you. 
The sudden onset of this issue in a home where it has not always been present is an indicator of some kind of damage to the property. This is usually in the crawl space or lowest level of a home. The most common cause will be a non-encapsulated crawl space or uncovered crawl space vents, but there are other potential issues that could be at work. 
The Stack Effect can be Dangerous 
Because of the way the stack effect increases airflow through your home, it can be dangerous for several reasons. First, this airflow from outside can bring harmful allergens and contaminants into your home or contribute to the spread of things like mold and mildew. This can cause respiratory issues and skin irritation, among other things. 
One of the most pressing issues, however, is the way that this can accelerate the spread of immediately harmful substances like gas. If you have a gas or carbon monoxide leak in your home, this kind of airflow will make it spread through your full home with alarming speed. Fire will also spread incredibly quickly when the stack effect is at work. 

It can be hard to know when the stack effect is at work in your home because it is a largely unseen occurrence. However, there are a few things you can be on the lookout for. 
Slamming Doors and Drafts 
The most noticeable component of the stack effect is the creation of a channel of air that runs throughout a home. This channel of moving air has many effects on a property, but the most visible and tangible are drafts. These will make it harder to maintain a consistent temperature in your home and put a strain on your HVAC. 
More than this, a strong draft is like to cause windows, doors, and shutters to slam when it picks up. If you notice that certain doors or windows are prone to slamming shut or open when left ajar, it is likely the stack effect is the cause. This is also an indicator that the room in question is close to the main channel of air running through your home.  
Increased Energy Usage 
One of the main issues with the stack effect is that it destabilizes the climate and environment inside your home. As such, you will find that the levels of relative humidity and temperatures inside your home fluctuate regularly inside your home. This is not just uncomfortable (and potentially unhygienic), but costly for you and your home. 
Humid air is, in and of itself, harder to heat and cool than arid air. As such, your HVAC system will struggle not only with the fluctuating temperatures in your home, but it will have to work harder when the air being brought in by the stack effect is humid. This will increase your energy consumption and, by proxy, your energy bills. 

Preventing the stack effect from affecting your home is a matter of identifying and repairing the issues that are letting air into your home in the first place. As we have stated, in most cases the issue is in the crawl space, but there are exceptions. 
Professional Intervention 
First and foremost, calling a professional to properly assess your home for signs of damage is important. The stack effect is very simple; it simply requires an entry and exit point for air at the lowest and highest parts of your home. Because of this, there are many potential sources and co-occurring issues you may have to identify and rectify. 
Crawl space professionals are far better placed to do this than the average homeowner. There is a chance, of course, that uncovered crawl space vents are the root of the issue. In this case, it will be easy to fix, but you should still have your home assessed for damage that may have occurred as a result of this exposure. A professional will be able to diagnose the causes and identify co-occurring issues and damage with ease. 
Crawl Space Encapsulation 
One of the easiest ways to deal with this issue is to fully encapsulate your crawl space. Not only will this cut off the necessary exit and entry points, but it will protect your home from other issues. By fitting vent covers, vapor barriers, and insulation you will not only remove the necessary conditions for the stack effect but also prevent dampness and humidity from getting into your home. 
This will have many long-term benefits for your home and your health. As well as preventing the constant airflow and movement created by the stack effect, encapsulation will prevent mold formation and dampness from taking root, and reduce pests’ interest in the crawl space. This will protect you from wood rot, damage to your crawl space joists, and sagging floors. 

Call Complete Basement Systems for Crawl Space Repair 

Because most properties have ventilation that allows air to exit at the highest levels, the main cause of the stack effect in a home is likely to be found in the crawl space. An entry point that allows large amounts of air to be drawn into your home from outside, such as an uncovered vent, may be all that is needed to disrupt the airflow and climate inside your property. Identifying and rectifying the precise source of this issue, however, is not always so simple. As such, we recommend that you bring in a professional to assess your home and implement an appropriate solution. 
DIY Doesn’t Work 
There are many DIY tasks that can be very successful, but we do not recommend that you try to investigate and fix this issue alone. First, it can be very difficult to find all the contributing factors when it comes to the stack effect at work in your home. In many cases, there will be a complex mix of issues to address. 
Even if you are able to find some of the contributing factors, you will have to address them properly. If the issue is an uncovered crawl space vent, the task will not be too large, but issues like floor and wall gaps and structural damage will be much more difficult to deal with.  

Professionals Give the Best Results 

Complete Basement Systems has been offering crawl space and foundation repair services to the residents of Colorado Springs and Denver, CO, for years. Our team is skilled, knowledgeable, and dedicated to providing every client with the best possible experience. We have a portfolio of excellent specialist, professional-grade products, and a reputation for excellence. 
If you’re ready to bring balance back to your property’s internal climate, contact us to schedule a free inspection and repair quote. Our inspections come with no obligation to book repairs through us and include a same-day written quote for the cost of our suggested repairs. We provide this so that you can shop around, fully armed with all the information you need. 

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