Category Archives: Infared Pictures

The Foundation of your Home: Slabs, Basements, and Crawl Spaces

What is under your home?  I hope you have some solid ground.  If you do great!  Now how did your home builder get to solid ground?

The first of a multi-part topic.
Left: Slab on Grade ready for walls. (courtesy of Wikimedia Commons)

That can be done with a slab on grade construction. It can be done with a basement.  It can be done with a crawl space. A home can use a combination of methods. It is not at all uncommon to see homes with 3 of the 3 approaches.

Above Right: A slab on Grade shows heat loss through the slab. This is under the front door. Inside temperature is 72 degrees, outside is 14 degrees. The cold (blue) pile is snow.

Basements are generally a below ground space that contain living area and is capable of being heated.  This does not include below ground spaces that are for storage or storm shelter. Basements may be full, view out, or walk out types.

Left: Typical craw space, showing rim joist. This has about 30 inches of concrete and a 2×8 floor joist.

Crawl Spaces are below ground space with no living area.  They are generally low head room spaces, hence the name – Crawl Space.  Some you can actually walk in.  I have seen several crawl spaces that are only 12 – 15 inches high, most are 30 – 48 inches high.  Crawl spaces generally have duct work for the HVAC system, plumbing, and wiring. Occasionally the furnace will be in the crawl space.

Below Right: This addition has 2×10 floor joists with support beams. It provides about 8 inches of clearance between the floor and the beam.

Many homes have a basement with crawl space. Builders in one geographical area tend to build with the same approach.  Another geographic area will find another approach being common. In places where the water table is only a few feet below ground you would be hard pressed to find a basement.  In places with large rock formations near the surface, the builder could use any of these approaches depending on how deep the rock is on the building site.  In tornado alley, basements are always welcome for a storm shelter, and some families use their crawl space.

How do these spaces impact the energy use in your home?

Depending on the age of the home, the below ground walls of the house could be of stone, block, rubble fill or concrete.  These are hard materials that have similar physical properties.  They have high thermal capacity; they will stand extended periods below ground in contact with dirt and moisture.

Thermal Capacitance

Thermal Capacitance is the physical characteristic of a material to hold heat. How long does an object stay hot after being heated? The longer is retains heat, means a higher thermal capacitance.

Above Right: The Rim Joist is where the basement window is. Note the heat transfer through this area. It is somewhat diffused by the brick veneer. Outside temperature is 20 degrees, inside temperature is 68 degrees about 10 pm.

Growing up in Southern Nevada, I lived in a house constructed of concrete blocks.  My bedroom was on the east side.  An 8 foot fence stood 4 feet from my bedroom wall. The sun did not shine directly on my bedroom wall until about 11:00 AM and by 1:00 PM it had passed over. I would go to bed at between 10:00 PM or 11:00 PM and the wall would still be well over 100 degrees. So that wall loaded enough heat during that 2 hour period, to still be over 100 degrees 9 hours later. If a material can hold heat like that, then it can also hold the absence of heat, or cold, in the same way. Concrete, and stone have a high thermal capacitance.

Any basement or crawl space wall will extend both above and below ground. It is not uncommon to see a wall 1 and ½ feet above ground and the rest below ground.  If that portion of the wall is un-insulated, the heat will flow through the wall. Heat will flow in during the summer and out during the winter.

The Infrared Image (Above Left) shows a concrete basement wall. The upper part is showing relatively cooler and the bottom relatively warmer. The mid-point of this image is about 4 feet below the top of the concrete wall. The outside temperature is 45 degrees. Imagine the difference at 20 degrees?

What can the homeowner or the builder do to these walls for energy savings?

Insulation is the obvious answer. What kind of insulation is a better question. I would specify the insulation, you choose, to be installed correctly, that it be durable and properly protected from damage.

Before we actually get the insulation, we need to make a stop.  Air movement through and around the insulation will significantly impair the effectiveness of the insulation.  So lets tighten up the area.  The first area to look at is the Rim Joist.

This is on the Rim of the foundation wall. The floor joists, 2×6 or larger or a truss system rests on the top of wall. If you look at any of your rim joist area you will see a number of things.

(Right) An IR image of a Rim Joist. Outside temperature is 70 degrees. This is a south wall and the sun has been shining on it. Lots of solar loading.

Usually your outside faucets come through here. The gas line enters the house at this point, the air conditioning copper tubing, and perhaps other utilities.  I’ve seen dryer vents installed here, and even the flues of conventional hot water heaters.  Those are usually easy to spot because the flue then goes up the side of the house above the roof.  If you have a tankless hot water heater, the PVC flue may well exit the area through the rim joist.  Then you have joints, knot holes and it is not uncommon to see actual holes where something was there and has been removed. All these holes and gaps need to be sealed up.

Remember that insulation does not stop air movement. Caulk is great for stopping air leaks.  You can use caulk straight from the caulking gun.  Some gaps, may need  backer caulk also called rope caulk.  This is ½ inch strands of caulk like material that you can push in by hand. Then come back over it with the caulking gun.  Smooth the caulk with a tool, or your finger to make it go a little farther, make it look a little better and to eliminate any bubbles that might have formed.

If the gap is larger you may wish to use some of the foam in a can. This one part expanding foam uses moisture to cure. Use along a rim joist would probably have enough moisture to cure properly. Take seriously the caution, to not wash with water if you get in on your hands or elsewhere.  Water will cure it.  It will take a couple of weeks to wear off.  If you don’t ask how I know that, I will not turn red in the face!

You can also use rigid foam on larger openings.  Just remember to caulk the edges.  Also remember to caulk the joint between the sill plate and the concrete. New builders use a gasket now,  a bead of caulk is always helpful.

If the rim joist has insulation, you can remove it to do the air sealing.  You can replace it after air sealing, just be sure to install it properly. It is most likely a fiberglass batt, it may have a paper backing on it, it may not.  The paper backing may be facing the inside or the outside. I’ve observed all these in the same house.  The paper backing is a vapor retarder. It should face the warm in winter side of the wall in this area of Kansas.  (Climate Zone 4)  The batt insulation should fill the space between the floor joists, the concrete rim and the subfloor. That space is probably 8 inches deep, 16 – 24 inches wide and 6 ½ to  24 inches high.  Most common would be 8x16x 7.5 inches.

Since the Rim of the foundation wall is usually 8 inches wide, that would allow, at R-3 per inch, insulation of R-24.  I see R-19 batts commonly used here, older insulation jobs or homeowner installed jobs will show R-13, or even R-11.   If you have a ceiling in your basement, you may only have access to part of this area.  You can work in the accessible area and make a difference.

To remove a finished ceiling and then replace after the air sealing and insulation is completing will probably not be cost effective, even if you do not consider the effort of the Do It Yourself labor.

This is the first of a multi-part topic. We will look at Basements, both finished and unfinished, crawl spaces, and slab floors each in more detail.

A Cold and Frosty Morning: What might an Energy Auditor Do?

Energy Auditing uses observation and science to determine what is happening in a home related to Energy Usage.  Necessary tools are a good flashlight, a blower door, and some way to record the observations for later analysis.

Optional tools, well – Energy Auditors can be come “Tool Junkies”.  Digital Dual Channel Thermometers, Spot Radiometers, Infrared Cameras, Computers, Software, Digital Cameras, Smart Phones, iPads, you name it, an Energy Auditor could probably find a use for it.  Then along comes a Cold and Frosty Morning and you are driving to your next audit. How do you make the most of your drive?

You could look at the roof of various homes as you drive.  On a couple of recent morning drives, I was doing just that. I stopped and shot a few pictures of different homes.  All of these homes were built between 1960 and 2000.  So here they are with comments. I have cropped the images to show just the roof, in most cases this will allow the home to remain one of many.

I have not audited any of these houses, and have only been inside two of them.


This frosty roof shows no frost along the roof line, directly above the exterior wall.  Note how it turns the corner on the hip of the roof.  I have outlined interesting points.   The vertical bar marks the point of the electric service, note the service line.  The lack of frost directly above this area is telling.


The issue here is that heat is being lost into the wall, and then through the top plate into the attic and then out the roof.  If you look at the area where the electrical service enters from inside the attic, you will find some type of holes in the top plate.  Perhaps a larger hole then necessary to allow the electric wiring.  A little caulk could go along way here.



Again the top plate of the exterior wall shows leakage.  Also in this image, an interior wall shows leakage in the upper roof area.

Heat loss occurs in interior and exterior walls.  Just caulking the outside of your home is not the best bang for you effort in sealing air leakage

This is interesting.  Without knowing the inside plan of the upper floor I am uncertain about the cause.  I would look for an attic access hatch, a furnace located in the attic, or perhaps some type of missing insulation along with a unique floor plan.

This picture shows the heavier frost over the eves of the home and less frost over the entire attic.

I would expect to find little insulation in this home, and what is there would be deteriorated in terms of effectiveness.  I would expect to find insulation moved or non-existent in several places.  I would also not be surprised to record a high leakage result from the blower door test.

Another picture of the top plate in an exterior wall.


This is an infrared image of the home with Frost pattern above.  I took this image at a different time then the exterior picture.  Both images are as is, no Blower Door going to exaggerate the air movement. It was also taken in the summer, so the heat coming in from the top plate leakage matches the heat escaping in the Frost Image.

Preliminary Conclusions:

Are these pictures definitive?  No, like most items on an Energy Audit, you need to look at several things to make a firm determination. Picture two is an interior wall, my knowledge of the homes interior, assists with this determination, even though I haven’t audited the home.

These are not necessarily a single look.  At least three of the homes, I have different pictures of different frost patterns.  What might make the difference?

  • Outside temperature and dew point differences.
  • Inside temperature differences.
  • Weather conditions; calm with little wind VS a steady wind of 20 mph or more during the 6 hours before and during the frost buildup.
  • Exposure:  These images have a western, or northern exposure. There may be differences.

What if I look at my house and do not see a pattern?  Look on another day, preferably several days.  The different conditions, may present different patterns.

Does a pattern like this cost me a lot of money?  Perhaps yes!  Perhaps no!  It depends.  To get more details get your Home Energy Audit. Each home is as unique as each person is.

Images like these only paint a picture.  We cannot determine how good or bad the heat loss is from the picture.  It provides a place to look, or not look.

If you take a picture of your Frost Pattern, upload it and put the link in a comment.  Let’s see what readers come up with.

Here are a few more with minimal comments.


Neat image with the Geese flying over.

This is a  most interesting pattern.  I have no idea what is causing this pattern. I would look for high air leakage, patterns on the ceiling with the IR during the Blower Door testing, and it would be interesting to look around the attic in this house.



Insulation: Properly Installing Fiberglass Batts

The last two posts have concerned issues of properly installing Fiberglass Batt type insulation.  That discussion revolved around newly installed insulation.  Inspections were done after the insulation was there and before the drywall was installed.

In this post, I would like to address some of the problems I see after the home has been in use.  The Batts in these cases were installed anywhere from 10 years ago to 40 years ago.  We all have experienced the issues of time. What changes does time bring to a Fiberglass batt?  This leads to ‘Why proper installation is so important.”

I have audited home that were built more than 100 years ago.  My friend Bud, has discussed auditing homes that are much older, 150 – 250 years. A home lasts a long time.  Every month the home gets Energy Bills.  Are the Energy Efficient Features of the home keeping those bills at the level they were planned?  If a feature was improperly installed, probably not.

Best Practices for installing Fiberglass Batt type insulation include:

The insulation must be in contact with the Air Barrier.  In our Climate Zone the Inside wall is the Air Barrier.

This means the batts must be stapled to the face of the framing material; not to the side.  If you have the batts stapled that way, then they are not in contact with the air barrier.  This is illustrated in the Infared picture. Note the cooler colors near the top that are rounded and follow the framing down the wall, and the dark hole in the top of one wall cavity.


Batts showing air movement, not in contact

Batts not incontact with Air Barrier

A Fiberglass Batt must be covered on each of the 6 sides.

This one seems simple, in an exterior wall, the top plate, the bottom plate, the drywall, the exterior sheathing, and the framing constitute all 6 sides of the batt.  Now think about the wall that is formed between the end of the vaulted ceiling and the attic?  OK;  Drywall, Yes!; Bottom Plate, Yes; Top Plate, not usually; Framing, sort of; exterior sheathing, usually nothing.  So, we have 2.5 on these types of walls. Below is a picture of the end of two knee walls with no framing on a corner of a vaulted ceiling.

Knee wall from Attic Side

Solutions on Knee Walls:  Cover the top, back and the sides of the batts at the corners with an encapsulating material.  House wrap installed according to manufacturers directions is a good choice for an existing home.  Easy to get into the area and then apply.

A Batt should not be compressed.

OK!  Think about all the things running in walls.  Electric wires, pipes, CAT 5 cable; phone lines, cable TV, security system cables.

Poorly installed Batt Insulation

Poorly installed Batt Insulation

First, you have the installs that are done before the insulation is installed; typically the electric and plumbing.  The insulator can deal with these easily. The batt can be sliced, partly through, to allow the obstruction to pass through the middle, instead of stuffing the batt behind or pushing the batt into place on top the wire or pipe. It can be carefully cut to allow an electrical box.

Good Installation of Fiberglass Batts

Good Installation of Fiberglass Batts

For those tradesmen that follow the insulator, everyone else on the list above, it is not quite so easy. If they come before the drywall is up, then you may find holes in the kraft paper, and wires compressing the batt as it runs from 2x to 2x; or you may find something else. If they come after the drywall, your guess is as good as mine as to what the wall will actually be.

The infrared image below shows air infiltrating around improperly installed fiberglass batts on the other side.

Infrared Image Infiltration in Knee Wall


If you are renovating a wall in your house, and you choose to insulate; fantastic!  It will save you money.  Lots of insulation choices available, if you choose Fiberglass Batts, follow these concepts and you will maximize the effectiveness of your insulation.


The only other item you should do, when renovating and insulating is to air seal and stop those cold drafts. That is a subject of another post!

Thermographic Imaging

If you’ve been reading about Home Energy Audits, you’ve probably seen a thermographic picture of a home. These color pictures show temperature differences. The windows show up as white or red, the walls show a darker color. They’ve even been part of some TV Commercials.

Earlier this month the National Standard for Thermographic Imaging was published. The purpose of a national standard is to enable two different energy auditors to obtain valid results with the camera on the same building.

The use of a difference in temperature to show where a house is loosing energy is very interesting. It can be skewed, if the picture is not, taken with a proper understanding of the limitations and potential external causes of temperature changes. Wind can cause a change in the temperature difference. Is the wind blowing from the East and you are taking a picture of the North wall, so some of the temperature difference is blown away. If the wind is from the south, is the difference increased?

The answers to these and other questions will be revealed for me this week. I will be in Manhattan at the Kansas Building Science Institute, working on my certification as a Level 1 Thermographer.

I will try to post some information during the class, so you can follow along my journey.