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14 Risks of Poor Attic Ventilation

14 Risks of Poor Attic Ventilation

The risks of poor attic ventilation in any roof installation mainly relate to the attic’s inability to create enough airflow to move moisture and heat from inside to outside of the attic. Preventing the attic from staying dry and free of moisture as it should be. Causing damage to the roof that shortens its lifespan, as it's meant to stay dry too, and can’t prevent the growth of mold, algae, rot, etc. within the home. That’s quite a problem.

How it works is that heat rises from inside the home when its occupants are cooking, running the dishwasher, dryer, taking a shower, etc. Assuming all exhaust pipes from appliances are routing outside of the home already, residual heat should be rising into the attic. With enough active and passive ventilation in the attic it should be able to release all of this without a problem as detailed in the anatomy of a roof.

In this scenario there is a lack of attic ventilation not allowing enough airflow, potentially blocked vents or dysfunctional active vents are in the mix, and leading to the following issues.

Major Risks of Poor Attic Ventilation

These are major risks of poor attic ventilation as they can potentially cause serious harm to the home and its occupants if not taken care of in a timely manner. As these problems exist beyond the roof system, the repairs will be extensive to bring the home back to being in good condition again.

1. Extreme Attic Heat in the Summer

A lack of airflow in the attic will cause air to become trapped in the attic, reaching temperatures of 150 degrees fahrenheit (65 degrees celsius) in the summer. Which will damage the roof’s shingles that are meant to remain cool in order to last long, and will heat up the rest of the home. As opposed to a climate-controlled attic which would remain the same temperature as outside of the home.

2. Condensation Buildup in Winter

When the roof is cold due to the outside temperature and the attic is trapping heat within it, causing the attic and underside of the roof to create condensation; Similar to a soda being put into room temperature and forming drops of water on its sides. This trapped moisture will prevent the attic and roof from staying dry, damaging the roof deck and its framing in the process.    

3. Shorten Roof Lifespan

A roof is meant to stay cool and dry to perform its best, with poor ventilation this is not the case so its lifespan will be cut short. Primarily due to the lack of airflow trapping heat in the attic coupled with outside temperatures. 

4. Ice Dams on the Roof are Likely

Ice dams are when snow melts, freezes and on the next melt, water gets trapped behind it; Major risk to the roof as its ice will make its way under the shingles, through the roof deck too if there’s enough space. Due to attic trapping heat in the winter it will cause ice dams to occur almost daily in the event of snow.   

5. Frost Forming in the Attic

Condensation that builds up in the winter will freeze overnight on the underside of the roof and the edges of the attic where condensation formed earlier. Causing nails holding the shingles to become frosted which will become rusted over time and drip water every time it heats up again. This will widen the nail holes, allowing leaks to start from the top of the roof. Also, this frosting and melting of frost in the attic will cause water damage to the roof’s framing, electrical wires and plumbing in the attic, while helping cause ceiling leaks in the process.    

6. Mold, Mildew and Rot Growth

Mold, mildew and rot each grow in damp environments like a poorly ventilated attic, and are a fungus that helps to break down any old materials back into soil. This will cause damage to any surface in the attic from its framing, roof deck, electrical, plumbing, etc. Notably, it will enable mold to grow exponentially faster, release toxic spores into the HVAC system and cause many respiratory issues for occupants. 

7. Bulging Walls and Musty Odors

Moisture buildup that recedes from the attic in the home will attach to the drywall and plastering. This Results in the plaster releasing a musty odor back into the home and the drywall will begin to bulge or misshapen to compensate for the moisture it has absorbed.        

8. Unwanted Pests Inside

A poorly ventilated attic will result in cracks to the exterior of the home allowing insects, rodents and other small pests to access your attic/home. These pests will eat through electrical wires, carry disease, eat through walls, get into the food storage, etc. If there are bats, certain species are under extinction conservation so the homeowners will not be able to evict the bats like other pest species.

9. Layered Shingles

When multiple layers of shingles are installed on a roof they will trap water and moisture in addition to that trapped in the attic. Causing damage from above the roof and below, drastically shortening the life of the roof while obscuring any leaks within its layers. Meaning there will be water damage that isn’t all too visible to the homeowner;

10. Roof Deck is Sagging

Where the moisture buildup in the attic has softened the roof framing/decking and has caused it to sag in places. As water begins to accumulate in these areas, they are likely to leak then lead to additional water damage. As long as a professional is able to repair the roof deck/framing, the roof will continue to live on, it’s not worth the homeowner injuring themselves over.  

Minor Risks of Poor Attic Ventilation

These are minor risks due to poor attic ventilation because these issues are isolated to the roof system for the most part. They are still manageable or early enough to repair without causing too much additional pain.

11. Leaks from Deteriorating Roof

As the roof deteriorates it will become less waterproof or be less capable of having water run-off it as it should. Causing water to accumulate on areas of the roof, which will lead to leaks.

12. Paint Will Peel

Trapped moisture in the attic will recede back down into the home’s interior/exterior since it has nowhere else to go, this will cause moisture absorption into anything it can attach to. This moisture buildup will cause the paint to blister and peel.

13. Rusted Fasteners Inside/Outside

Fasteners like nails, brackets, mounts, etc. will inevitably rust due to the excessive moisture buildup. This rust will be dangerous if water carries it into contact with exposed electrical wires. Otherwise it will loosen its hold and allow the holes that it's created to leak.  

14. HVAC Overworked & Shortened Lifespan

HVAC will have trouble moderating the temperature as it will be too hot or too cold the majority of the time, forcing the HVAC system to be working all of the time. A telltale sign is when different rooms in the home have different temperatures as the HVAC system is unable to keep up with the home’s demands. Eventually, it will need constant repairs and need to be replaced at some point.  

Conclusions About The Risks of Poor Attic Ventilation

Attic ventilation is meant to create enough airflow in and out of the attic to ensure moisture and heat are released easily from the home. Alternatively, if there is poor attic ventilation, it puts the roof and home’s lifespan at risk.

As a homeowner it's important to take care of the entire roof system; attic, ventilation, roof and gutters. It's all or nothing, when one is in disarray like attic ventilation this prevents the roof from insulating and protecting as well as it should. 

Primarily, poor attic ventilation causes the trapping of moisture and heat which will lead to various kinds of water damage, and mold along with respiratory issues for its occupants. While affecting each of the home’s vital systems at the same time; electrical, plumbing, foundation, framing and HVAC system.

Taking preventative measures to bring the attic ventilation back into working condition will save the homeowner all of this trouble in the long-run, at a relatively affordable investment.  


What are the risks associated with poor attic ventilation?

Inadequate attic ventilation can lead to excessive heat buildup, moisture accumulation, and reduced energy efficiency, causing premature roof deterioration and potential health issues.

How does poor attic ventilation contribute to heat buildup?

Insufficient airflow traps heat in the attic, increasing indoor temperatures and putting extra strain on cooling systems, which can raise energy bills.

What problems can arise from moisture buildup in an inadequately ventilated attic?

Moisture accumulation can lead to mold growth, rotting wood, and degraded insulation, compromising structural integrity and indoor air quality.

What impact does poor attic ventilation have on roofing materials?

High heat and moisture levels can cause shingles to deteriorate prematurely, reducing their lifespan and requiring costly repairs or replacements.

How can homeowners prevent the risks associated with poor attic ventilation?

Installing proper ventilation systems, including intake and exhaust vents, can maintain balanced airflow, regulate temperatures, and mitigate the potential risks to the attic and home

BulletpRoof Roof Systems is family operated roofing contractor with over 15 years of experience. We have been helping families throughout Mission, BC and neighbouring areas resolve issues with their residential sloped roofs for many years now. We pride ourselves on providing genuine professional roofing services and are dedicated to helping our clients resolve issues with their roof systems as efficiently as possible.
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