New home insulation is not only about insulating, but also about sealing your home. Homes need to keep the warm air in during winter and keep the cool air in during summer. This is done with insulation and air sealing.
Insulation is not enough on its own. If your home leaks air, the insulation cannot properly do its job. Houses today need to be air tight. This can be done with certain insulation types and a combination of air sealing products.
We are going to cover the following topics in this blog post:
- Passive House Design
- Do houses need to Breathe?
- Mechanical Fresh Air
- Cavity Insulation & Continuous Insulation
- R Value and U factor
- New Home Insulation Types
- Windows and Doors
- Blower Door Test
Passive House Design
Today, we are building houses on the Passive House Design concept. Passive House has 5 key points.
- Continuous Insulation / High Quality Insulation
- Air Tight Construction
- High Performance Windows
- Energy Recovery (Mechanical Fresh Air)
- Solar Heat and Solar Shading
Do Houses Need to Breathe?
Houses do need to breathe, but houses should not breathe through walls, they should breathe through controlled mechanical means. People are often concerned with air tight houses not being able to breathe. Houses do need fresh air and need to deal with humidity, but this should happen mechanically with proper equipment. Your house should not breathe through leaky walls. It is just ridiculous for people to think walls should breathe. This is such a disproven theory of construction. In my opinion, breathable house wraps are nonsense products that should be eliminated. Breathable membranes for homes are not truly water proof and will not keep your conditioned air inside your house. Do not use breathable house wraps or membranes.
Mechanical Fresh Air for Homes
I really want to dispel the obsolete idea that a house should breathe through its walls. A breathable wall really is nonsense by today’s standards. If you follow the passive house standards, you would use an ERV to do the job of breathing. This is a piece of mechanical equipment that brings fresh air into a house and exhausts old air from within the house. The ERV also uses the heat from the exhaust air to preheat the new air, saving energy. It can also pre-cool of course as needed.
Below is a photo of an ERV in a house we did. It is a strange looking device, but it is very important for energy efficiency. I highly recommend using this type of equipment for building a sustainable home.
New Home Insulation And Air Sealing
Difference Between Cavity Insulation & Continuous Insulation
There are 2 insulation methods we need to understand. Cavity Insulation and Continuous Insulation. Continuous insulation is a newer concept. Most older homes have cavity insulation. The difference between cavity and continuous insulation is simple. Cavity insulation is placed in sections of a wall, and continuous insulation is continuous around the entire home.
Cavity insulation is insulation placed in sections. For example if you frame a wall with wood or metal studs, you fill the empty cavity between the studs with insulation. This is cavity insulation, because the insulation is not continuous.
Continuous insulation is insulation that continues along an entire surface without interruption. This is done by putting the insulation either on the outside of the structure or on the inside of the structure but not within the structure like cavity insulation.
R Value and U Factor
R Value and U Factor are terms for identifying the value of an insulation product or assembly. U factor is the inverse of the R Value. The higher the R Value, the more insulation value you have. The lower the U Factor, the more insulation value you have. U Factor and R value give you the same information in 2 different ways. Typically Windows and Doors are listed in U factor, and Wall insulation and Roof insulation are listed in R Value.
New Home Insulation Types
- Rigid Insulation
- Spray Insulation
- Blown In Insulation
- Batt Insulation
Rigid Insulation for New Homes
The most common form of continuous insulation is rigid insulation. Rigid insulation is a sheet of insulation. Two of the types are Polystyrene and Polyisocyanurate (Polyisocyanurate has a bit of a higher R Value). Rigid insulation is the most common form of continuous insulation. Aerogels are a rigid insulation that have the highest insulation value of any material on earth. They are also quite expensive.
Common Examples Of Rigid Insulation Continuous Insulation
- EIFS Exterior Insulation Finishing Systems
- SIPs Structural Insulated Panels
- ICF Concrete Insulated Forms
- Rainscreen with Exterior Insulation
- Insulated Metal Wall Panels & Roof Panels
EIFS Exterior Insulation Finishing Systems
Exterior Insulation Finish Systems or EIFS is where you put rigid insulation on the outside face of a building in a continuous installation and then put a finish material over it. One common method is gluing the rigid insulation onto the exterior sheathing of a house and then applying stucco over the insulation.
Rainscreen with Exterior Insulation
A Rainscreen is a type of EIFS. This is where you have exterior insulation and a face material over the insulation. The face material can be wall panels that are not exactly the waterproof surface of the building. The waterproof surface is over or under the insulation layer as a membrane.
SIPs Structural Insulated Panels
Structural Insulated Panels or SIPs are prefabricated panels were a rigid insulation sandwich panel is made and is the structural bearing wall for the house.
ICF Insulated Concrete Forms
Insulated Concrete Forms or ICF is a product where concrete forms are made of rigid insulation. You pour the concrete into the forms and the forms stay forever as part of the wall. You then apply a finish material on the inside and outside of the walls. We have another blog post you may want to check out on Concrete House Design.
Insulated Metal Wall Panels & Roof Panels
Insulated Metal Panels are prefabricated metal sandwich panels that are attached to the building framing. The panels have rigid insulation on the inside, and a metal face for the exterior facade of the building.
Spray Insulation Types for New Homes
We all know insulation is important to reduce your energy usage in heating and cooling, but if you build a new home with a great deal of insulation that is also leaking air, you are not getting a great value for all the insulation in the house. Spray insulation is a foam that is sprayed in between your wood or metal studs. This foam expands and gets into all the cracks, holes, and joints around windows, doors, or anything else in your walls, floors, or roof. Anything going through your insulated surface, be it a door, window, pipe, exterior lights, exhaust vents, to name a few, create weak points to your air sealed house, as well as cracks and construction flaws. The goal is to make sure the conditioned air inside your home does not escape through your walls.
Spray Insulation Types
There are two kinds of spray foam insulation: Closed Cell and Open Cell.
Open Cell Spray foam Insulation:
- Open cell spray insulation is more affordable than closed cell insulation.
- Open cell insulation has an R-value of typically R-3.5, or a little more per inch.
- Open cell provides air sealing keeping the outside air out and the inside air in.
- Open cell is not water or vapor resistant.
- Open cell has no structural value.
Closed Cell spray foam Insulation:
- Closed cell spray insulation is more expensive than open cell spray insulation.
- The R-value of a closed cell insulation is typically R-6 to R-6.5 per inch (that is a very good R value).
- Closed cell provides air sealing, keeping the outside air out and the inside air in.
- Closed Cell insulation is also vapor resistant water resistant and will not allow vapors, humidity, water to pass through it.
- Closed Cell insulation is denser, heavier, and stronger. Closed cell is the only insulation that will actually add structural value to a wood or metal framed wall or roof. It adds rigidity and stability to the framing of the house, increasing the entire overall structural value.
Economy is obviously an issue. Although closed cell is more expensive, it does have several advantages as we see in the list above. Also, realize you will need less closed cell insulation than open cell to achieve equal R-Values.
Blown In Insulation
Blown in insulation is more for existing homes where it is difficult to get into certain areas. This is not going to seal your house or provide vapor barriers.
Batt insulation for new homes is just about the lowest quality of insulation. I say low quality, because it does not serve more then one purpose, whereas other insulation types can also seal and waterproof. Batt insulation is the more affordable option, but it will not seal your home. You may need vapor barriers depending on where you are. If you are in the north (areas that get cold), put the vapor barrier on the inside. If you are in the south (areas that stay warm), you put it on the outside. You will also need to find a way to air seal the house.
Windows and Doors
Windows and doors need to be insulated and air tight. Below is a photo of a triple pane insulated and thermally broken window. The thermal break means the exterior face and interior face have a thermal barrier or thermal disconnect that prevent heat from passing through the window frame.
Blower Door Test
How do you know your home is air sealed? Blower Door Test!
We often test the homes we build for how well air sealed they are, and this is done with a blower door test.
A blower door test is a system for measuring air leakage through pressure and flow. Simply put, it is done by putting a plastic cover over a door with a fan in it. The fan blows air into the house, and a pressure monitor detects the rate the air escapes by the differential in the air pressure. This is a great way to know if your house is performing well in the air sealing department.
Insulation In New Homes
Our goal here is to make sure you understand that if you put a ton of insulation in your new home but the house itself leaks air, you are not getting the full affect of the insulation. Be mindful of these issues, as we are all trying not only to save a little money, but pitch in any way we can to help the environment. Higher quality insulation may bring a higher upfront cost, but the long term savings are huge. Savings on energy will be great, and saving our environment is priceless.
Thank You for reading our Blog Post on Insulation In New Homes
Please feel free to post questions or comments below. If you are interested in discussing a specific project that you are planning, please contact us directly to speak with an architect.
This post was written by Jorge Fontan AIA a Registered Architect and owner of New York City architecture firm Fontan Architecture. Jorge Fontan has earned 3 degrees in the study of architecture including two degrees from the City University of New York and a Masters Degree in Advanced Architectural Design from Columbia University. Jorge has a background in construction and has been practicing architecture for 15 years where he has designed renovations and new developments of various building types.