Air Temps vs Surface Temps
There are a various things that can affect the air temperature inside of a non-conditioned building, but typically there are two main factors: the amount of heat entering the structure (heat gain) and the amount of airflow passing through (ventilation). While these two things are independent of one another, when they are controlled and working together, they make the biggest impact on making the building cooler and more comfortable. The video below explains the relationship between the two and how radiant barrier addresses both.
Gaps for Airflow
Ideally you want to give the air in your structure a free, clear path to flow around the foil installation. Air movement is important for regulating air temperatures (see video above) and also for keeping the building dry (i.e. preventing any condensation from forming).
By leaving some gaps in the installation, air can easily move around the foil – in other words, proper ventilation can take place. The hot air in the building will travel the path of least resistance to make its way out of your building. When you install WarehouseFoil™ with the proper air gaps, it allows for maximum ventilation between the roof and the foil and it also gives you the benefit of full coverage. Here are some basic ventilation tips:
- In vented buildings, perforated radiant barrier foil is preferred.
- Ventilation is key to lowering air temperatures in your building.
- Seal any conditioned areas inside the building up, air tight.
- Don’t block venting with foil, or other insulation materials.
Ventilation & Moisture
The key to managing moisture in a metal building is proper ventilation in the areas that are vented and proper air sealing in the conditioned areas (when applicable). To be proactive toward these potential problems, it’s important to keep your building both cool and dry.
The idea behind ventilation is quite simple – don’t over complicate it. You need intake vents and exhaust vents; intake should occur at the bottom of the roof and exhaust vents should occur at the top since this is in line with natural airflow (warm air will naturally rise). This natural flow allows for moisture to freely move about and eventually diffuse. Incidentally, this is why radiant barrier is perforated and why you should always use a perforated product in a vented space. The perforations in the foil are tiny pinholes that allow water vapor molecules to pass through. This is exactly what you want: moisture moving freely to contribute to an overall dry building space.
To further help air movement, make sure you cut away any foil under vent holes in the roof – no matter what type of vent. Give it about 3 – 6″ of clearance around the opening to ensure even and easy air movement beneath the vent.
Do I Need More Ventilation?
You certainly want adequate ventilation, but more is not always better. Having good ventilation helps to reduce the air temperature, while having a radiant barrier helps reduce the surface temperatures. This is why radiant barrier combined with proper ventilation works to make your building more comfortable and energy efficient. From our experience, most people have a good amount of exit vents, but not nearly enough intake vents.
If you have several points of exit for the air, but not enough intake vents, then some of those outtake vents can actually turn into intake vents, completely disrupting the natural cycle of airflow. Air always travels the path of least resistance so by mixing exhaust vents, you can actually have the strongest vents dominate as the outtake and all other vents will become a point of air intake.
Again, this is important because the natural airflow is for air to enter the space down low, and flow out of the top. Your best bet is to make sure you have plenty of clean and obstacle free vents. In a non-conditioned building with radiant barrier below the roof, it’s perfectly acceptable to expect the air temperature inside the building to be within 10-15 degrees of the outside air temperature. On a hot, sunny day – that is a big difference!