The Unvented Attic Space


The relatively easy access to most attics (does not include any version of a finished attic so, if you have a second floor that would typically be an attic, this does not apply to you unless you wish to do demo before us foaming it) combined with the quest for ever-greater energy efficiency has led to a tremendous demand for improved insulating products, such as spray foam.

The ever-rising cost of construction has also seen many architects and designers attempting to make the most out of every inch of space (think home office, home schooling, parents needing temporary/ ongoing housing). Attics that cannot be used as living space is wasted space in the eyes of many.

This has led to the popularity of unvented attic constructions. Some designers intend this space to be used as extra bedrooms, playrooms, or as a means of placing equipment (such as HVAC units) where it will not take up valuable floor space.

Unvented attics also offer substantial energy savings when combined with spray foam insulation.

 

Unvented Attic Construction

 As the name implies, an unvented attic differs from a typical attic in that there is no uncontrolled natural venting space instead you have ventilation from your home and a 95% reduction in heat loss!

The unvented attic will retain heat in the winter and keep heat out in the summer creating a much more comfortable home with less differential from floor to floor, longer times with the furnace off and less need for cooling this summer!

 

Temperature and Moisture Control

 If your unvented attic contains the HVAC system and/or ductwork for your home, the HVAC unit will benefit from having a supply and return air “leakage” within the attic for climate control.

Setting up HVAC for an unvented attic with us is critical to the success or failure of your new space in your home! Don’t rely on those DIY kits for the foam! You might be lucky and get the mixture correct but if you don’t understand how to properly setup the HVAC system, you might end up with problems.

A good plan is critical to the performance of the spray foam and comfort of your home. Unvented attics must have the spray foam layer applied continuously, at a specific thickness, from the rooftop to the wall intersection and down the wall itself.

 

Insulating the Unvented Attic

 Nearly all heat loss occurs through the attic (Hot air rises!). Therefore, improving the air sealing/insulation in the attic (top of the structure) will result in a 95% reduction in heat loss and energy savings for the homeowner.

Unvented attics are best insulated and are completely sealed when the underside of the roof deck and attic walls are insulated with spray foam.

Using spray foam on the underside of roofs in unvented attics has been a common practice since at least the early 1990s.


If your home has complex coffered ceilings and numerous holes in the ceiling for lights and wiring, it would be next to impossible to seal the ceiling on the uppermost floor of the home. By applying spray foam to the unvented attic, you can achieve airtightness that acts as a perfect thermal barrier.

 

Why Choose Spray Foam?

 Spray foam is the preferred choice of insulation in unvented attics by contractors and homeowners alike.

Applying spray foam effectively seals even the most complex of attic assemblies, serving as both the thermal and vapor control layers, whether the construction is new or old.

Keep in mind that all wood-to-wood joints in the frame must be sealed so spray foam will be airtight when applied to the under the roof decking and between framing elements.

Attics that have typical ventilation in humid climates (such as a typical Philadelphia summer) have dramatically higher moisture levels than unvented attics, which is one reason why you see so many unvented attics here. When the attic is unvented and is completely sealed, not only are moisture levels cut to a bare minimum, but temperatures are also far more reasonable.

If you ever have any doubts as to just how effective spray foam can be in an unvented attic- you should measure the temperature in your attic in the middle of an average day. You can choose winter or summer, either is fine.

Take that same thermometer and measure the temperature inside an unvented attic with spray foam insulation.

 

The Bottom Line

If you have an unvented attic in your home or if you are building a new home and considering adding an unvented attic to your plans, you will want to take advantage of all the energy savings, not to mention the comfort levels, that spray foam insulation can provide.

As I always say, Comfort is only a FOAM CALL AWAY! Perhaps I should add that energy savings is also a FOAM CALL AWAY!

If you have any questions or if you are considering spray foam insulation, don’t hesitate to give the professionals at Spray Foam Insulators a call today 215-493-3677