Written by Eric Gans, Building Analyst & Envelope Professional I have completed over 1500 energy audits in Maryland which essentially means over 1500 trips to an attic.
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In Maryland, it is recommended that our attics are insulated to R-49
If you are having comfort issues in your home there is no doubt that a good place to start looking for answers is in the attic.
Maryland attic insulation projects can be better understood and considered with a little effort and knowledge.
To get things going you must identify two main things:
1 What insulation material exists up there now to figure out the R-Value per inch of what you already have (use the guide below)
2 Determine the insulation level in inches and general condition to calculate the R-value (download the spreadsheet)
Once these two steps are complete, you can determine if you are meeting current Maryland insulation building codes.
Before Getting Started - A Few Basics
What is the R-Value? The Answer in "Lay" Terms
R-value is the conventional method by which the performance of insulation is measured.
Insulation has one job - to resist heat flow. The higher the R-value, the better the insulation resists the transfer of heat.
Attic insulation can have a huge impact on your overall comfort, energy bill and HVAC performance. A well-insulated attic can make an old heat pump or furnace seem like it is brand new if the project is managed and installed right!
Maryland attic insulation is very important because in summer, it is responsible for stopping the hot attic air from coming inside (it gets 150 degrees in attic!!) and in the winter it keeps the warm conditioned air from going outside (through the ceiling mostly, due to pressure).
The attic is the most important place to check first, however there are other areas that should also be considered such as the basement, overhangs and crawl spaces.
Insulation R-Value requirements in the State of Maryland
LOCATION....REQUIRED R-VALUE MARYLAND
Typical Places You will Find Insulation
Attic Flat..................................................................R49
Attic Slope..............................................................R38
Vertical Wall (basement, crawl space, knee wall)..........R13
Crawl Space Ceiling..............................................R25
Below Cantilever....................................................R25
Rim Joist (top of foundation wall in basement)...............R19
Step 1 - Determine what Type of Insulation You Have
Different attic insulation materials yield different R-values based on how many inches are in place. So, an important piece of information to determine your insulation R-value is to identify the type of insulation that was installed in your attic.
Fiberglass batts, loose fill fiberglass, loose fill cellulose, mineral wool and two-part spray foam are all insulation materials that you might find in a Maryland attic.
Need help with this?
Pop your head up in the attic and take a photo of your insulation or if you live in Maryland get a comprehensive home energy audit through BGE or Pepco.
You can also call or email it to me so I can take a look and identify it for your eric@hometrustremodeling.com or refer to the photos below to try and figure it out.
Identifying the Most Common Maryland Insulation Types
Cellulose Loose Fill
General Characteristics
Grey in color
More dusty and clingy than other materials
Has bits of newspaper in it
Good fire/mold retarder w/ additives
Rolled Fiberglass Batt Insulation
General Characteristics
Typically referred to as batt insulation
Has the kraft paper or aluminum foil on one side
Recognizable due to the "Pink Panther" commercials
Must be installed flawlessly (unforgiving)
Low R-value per inch if not installed properly
Fiberglass Loose Fill
General Characteristics
Typically white shreds, pink squares or yellow shreds.
Much less dusty
Lower cold weather performance than cellulose
Different Insulation Types = Different R-Values
Once you determine your insulation type it is time to figure out the material's R-Value.
R-Value is sometimes misleading because several factors will have an impact on R-Value, including:
Step Two: Calculate a Reasonable R-Value Based on Your Attic's Overall Condition
Insulation levels in a Maryland attic are rarely the same everywhere. In order to gain an true perspective on how much insulation an attic needs will depend on what condition the existing insulation is in and what the levels are throughout the attic floor.
Un-insulated Areas Play a Heavy Hand in Poor R-Values
Now lets go a little deeper and explore the impact an un-insulated surface has on the entire area when it comes to overall R-value. If you go in your attic and see any area that does not have insulation, you should really pay attention to the information below.
To demonstrate the impact having no insulation has on the overall R-value, I am going to use a common set of circumstances in a typical Maryland attic.
For this example, the attic area in the home pictured above is 975 square feet and flat (R-49 recommended in Maryland).
At the attic floor you see 1" of loose fill fiberglass insulation (white stuff in photo below) and 7" of rolled fiberglass batting laid on top.
R-Value for the insulation in this Maryland attic = R17 (using this guide)
Here is the catch...
There are two major un-insulated areas in this attic (very common in our area).
1. A three foot by three foot push up hatch
2. A three foot by three foot whole house fan
Equaling a total of 18 square feet of un-insulated area at the attic floor.
This equates to just about 2% of the overall attic area (18 divided by 975).
The hatch from the attic has a plywood cover (seen in background)
Whole house fan as seen from the attic.
When calculated using the Home Energy Score Averaging Calculator it is clear that un-insulated surfaces can have a negative impact on the overall performance of your insulation.
A 975 square foot attic with 18 square feet of missing insulation reduces the R-Value from 17 down to 13 - for the entire attic!
Calculating the actual area with insulation in combination with the areas that are not insulated yields a significant reduction in overall R-value as seen in the two scenarios above.
Conclusion: if as little as 2% of your attic surfaces are un-insulated it can have as much as a 25% negative impact on the overall R-Value of your current insulation.
What does this mean in the easiest to understand terms?
If you are missing insulation in as little as one or two areas of your attic, your overall comfort and energy bill will suffer!
