I have written about ventilation for years concerning commercial masonry wall sections and the benefits of the products in conjunction with air and vapor barriers, WeepVents and weep placement. Today I am going to look at ventilation from a residential point of view, relating to single and multi-story homes. Over the years, architecture ventilation concepts have improved, and so have the ventilation results.
Much has been published recently about the importance of ventilation and air movement in the cavity wall section. As a veneer heats up, the moisture and warmer air that is present in the cavity can be drawn up to the top of the cavity, where a WeepVent can be properly placed as a way to ventilate the cavity; the WeepVent is placed at the top of the veneer just under the soffit. If the weeps are properly placed, then hot moist air can escape from the cavity during periodic times in the day as sunlight and temperatures heat up the veneer. In cases where weeps are not at the top of the wall, then the soffit, which is typically attached to the outside face of the veneer, will allow the moist warm air in the cavity to flow up through the soffit overhang and into the attic space in the gap between the roof joists and the ceiling joists. The small gap is created when the building is framed, and the “birdsmouth” cut creates a small gap between the top of the ceiling joists and the rafter connection. This small opening will allow for continued air movement and ventilation.
When my home was constructed in 1975, the builder installed gable vents, soffit with holes at various intervals (but not everywhere) and vents near the ridge board for hot air to escape. In older homes where attic insulation has been installed, it is important to evaluate if the blown in or Batt insulation is blocking the gap between the soffit and or the top of the ceiling joists. Typically, this area was designed to be open, so the air that moved through the soffit flowed into the attic space and out through the roof vents eliminating moisture and heat from the attic. Since heat rises, the soffit will allow the air movement to flow through the holes, up in between the rafters and out through the roof vents that were constructed when the house was built. The gable vents do not assist in removing hot air; they are designed to draw in air so the attic can be vented. If any of the designed vented areas are blocked, and I believe in old and new construction it is very possible, then the hot air in the summer attic space will cause your heating, ventilation, air and cooling system (HVAC) possibly to be working less effective due to circumstances that often barely go unnoticed.
Unfortunately, the remedy for this is to open up the top of the soffit to allow air into the attic by removing the insulation that may have blown, shifted or settled during the life of your home or new construction mistakes. Baffles, found commonly at all building supply stores, can be made of entangled mesh or foam board and are a good solution to keeping the soffit/rafter space open for the life of the structure since they are not an expensive fix.
On newer homes built over the past few years, ridge vents are now commonly placed on the ridge of the roof, allowing ventilation to occur without any type of mechanical means. For this vent to function, the vents, once placed at the top area of the roof, must be sealed as they will not increase the ventilation, rather they will create a circulation where hot air is kept in the attic and not become properly ventilated, in addition, the gable vents of the past are typically not installed any longer as they have the same effect as the vents placed near the ridge board.
Why does any of this matter? Well, as we all pay higher amounts of money for everything, we still want to be comfortable. Though the issue of a hot attic in the summer seems to maybe be ridiculous, a hotter than it should be attic can be costing you money, wear and tear on your HVAC system and reduce the lifespan of the roofing materials.
So, it would always be a good idea to install WeepVents at the top of every veneer. They do not need to align with the flashing vents. I put them every two bricks because they give more ventilation this way. Besides, you will never see them again once you install them unless you clean by bucket and brush method; then, that will probably be the last time you ever notice them.
In a colder climate, these principles still apply. It is important to allow the movement of air to properly pass through the attic space and back into the atmosphere. The question still is, will the cold air over the ceiling or on the attic floor cool down the interior of the house since you allowed it to come in from the soffit? Well, no, it should not be a source of concern if air if the attic is properly insulated. Allowing the air to ventilate will help eliminate moisture, heat and the overall comfort of the home to be much better.