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Eric Gans
Certified Energy Auditor

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Residential Comfort & Energy Efficiency

Friday, April 03 2020

As a home energy auditor, one of the rewarding aspects of the job is to help homeowners uncover sources to their energy usage concerns.  It is especially gratifying when the energy audit was scheduled specifically to diagnose the issue before any big ticket decisions are made to try to solve the problem such as replacement windows or high efficiency heating and cooling unit (HVAC).  A well done energy audit can help you prioritize projects around the home in a way that guides you to getting the best return on investment.  If nothing else, you can make an informed decision to spend money on an improvement that will not yield an expected result.  Getting an energy audit puts you in the driver's seat.

There is one very good example of a common issue that I come across all of the time that is simply overlooked.  Expressed as a percentage, I would say that 90% of the homeowners I meet do not give this problematic area much thought, if any thought at all.  In order to get why the issue is such a problem there are two concepts that must be understood.

1. Stack Effect - A Building Science Principle

The first is the stack effect.  The stack effect is a building science principle that basically says that your house is kind of like a chimney in winter months.  When a chimney is in use, the fire is at the base pulling in oxygen to keep the fire alive (negative pressure) and as it heats the smoke rises and billows out of the opening at the top (positive pressure). You do not have to have a chimney in your house for the stack effect to be in play where your live.

When the heat is on during cold days, the warmer air that you are paying for rises like the smoke in the chimney.  Of course, the smoke leaves at the opening at the top of the chimney and so does your precious warm air.

How does this work in a house?  Imagine a bunch of smaller holes around the ceiling of you top floor where the warm air can sneak through.  Warm air escapes through the cracks and holes at the ceiling (positive pressure) which creates a pull pressure at the base of the building (negative pressure).  The stack effect essentially creates a conveyor belt where the belt moves the hot air out up top and pulls the cold air in down in low places (basement, crawlspace).
 

Stack Effect/Chimney Effect
Big inside/outside temperature variances (Delta T) increase the pressure dynamics in a building.


2. Bathroom Exhaust Fans - Dampers

Let's shift gears and focus on the exhaust fan in the upstairs bathroom.  Why the exhaust fan?  Let's think about that for a second.  Take a look at this diagram.

In theory, when the fan gets turned on, the air gets pulled in at the base of the fan and through the blower and into the duct that extends away from the fan to the "outdoors".  Unfortunately, this is not happening in most homes that I visit.

What's the big deal?  Besides not properly getting the moisture beyond the insulation in the attic to prevent mold and other health/safety concerns, there is typically another problem that is overlooked.

Notice where the air is flowing out of the fan in the photo above.  There is a little flap there known as a damper.  When the fan is not in use, the damper closes to prevent the communication of air between the two parts of the home (bathroom/attic).  If the damper is missing or not working properly, the fan becomes a gateway to the attic allowing the stack effect to overwork your heating system which leads to a shorter life, high bills and comfort issues.

This older bath fan in the attic does not have a duct running to the "outdoors".  It is also missing a damper which creates a gateway between in the inside of the house and the outside of the house.  Remember, the attic is part of the outside when there is insulation at the attic floor which is the case for most houses in Maryland.


The larger the gaps for air to leave out of the top of your house, the easier it is for cold air to get pulled in down at the base of your home. This pressure flow through the house is responsible for drafts, cold bathrooms, high energy bills and in extreme cases, moldy attics.

Leaky damper.  Large communication point between the attic and the inside of the house.

If you are not sure if your fan vents to the outside, one easy way to see is to take a look at your roof to see if you have any vents that look like the ones below.  If you see these, there is a good chance your exhaust is venting properly.

Another way is to go in the attic and take a look for yourself.  Here are a few more things to look for.

The upstairs bath fans in this attic have ducts connected to the actual fan, however they are not properly vented to the "outdoors".  The builder simply ran the duct to the ridge of the roof. but stopped short of sending them to the "outdoors".

 

Properly insulated and vented bathroom exhaust fans through the roof with exterior damper kit.
There are so many reasons why those that have a home energy audit done are so glad they did.  Most homeowners are aware of the big things that can help with energy efficiency, such as windows and HVAC.  But, there are less obvious things that are costing you money and getting an energy audit will uncover them for you so you can decide what to do.  

This newly installed fan is in the process of getting a duct installed to run to the "outdoors".  Air sealing around the fan is also key to improve the energy efficiency and comfort of a home.

As much as 40% of a home's energy use is related to HVAC so the idea is not to replace HVAC.  Rather, it is to reduce the amount of time you need to use your HVAC.

A home energy auditor can discuss better options like air sealing and insulation.  We can guide you to prioritizing the right projects. If you are going to spend the money to improve your energy bill or comfort or both, wouldn't it be nice to know that your decision is informed and will yield the results you are hoping to achieve?

Wednesday, April 01 2020

One of the keys to performing a good energy audit is to be consistent.  Consistency, yields high quality results for the homeowner. Having a sound routine and being sure to go through that routine for each and every house will serve the most seasoned home energy auditors very well.

One very nice experience as an auditor is to find things for people that are so easy to fix they could do it later in the afternoon after the audit is complete.  And, for very little money.  Each and every audit I make it a point to inquire with the homeowner about why they contacted us.  Is it because of a specific problem you are experiencing?  This helps me narrow some of my searching because it gives me good insights in to where to spend my time looking.

This leads my to a find I made at an audit Davidsonville, Maryland.  For an auditor, it is a fairly common issue, although some of the time it is more hidden and less obvious and could be missed.  On this day, the homeowner mentioned that one of the reasons they called is to figure out why the kitchen is so cold.  They moved in last summer (June) and now it is January and the experience has prompted a call to figure out what is causing the problem.
 

Front of the home.
 
As I began the audit and started outside to take a look around I began to get the overall picture of the house now that I was inside and did a full tour throughout.  I made my way around the side of the house to the kitchen area.
 
 
Two things stand out to me right away.  One thing to note there is that the kitchen is at the back corner of the house above the garage.  The kitchen window above the sink is the window that can be seen in this photo above the garage door.  The general area is inside the red lines.
 
The second thing that is is less obvious and is something that will require additional investigation is the exhaust hood just above the grill to the right of the sunroom.  
 
For the most part, and of course this is something I mentioned to the homeowner, the problem is never only one thing.  There usually are several things working against you and the ideas is to wrestle the power away from as many of those problems that you can in, order of how much they cost, in order to make the problem less of a problem.
 
So, treating the ceiling of the garage with a proper pressure boundary in addition to the thermal boundary would be a significant part of a project that was going to seriously attack the kitchen being cold.  But, in this case the example that I will demonstrate here can be seen in all types of houses and perhaps this might be the only source to your issue.
 
Let's get back to the exhaust hood on the back, above the grill and next to the sunroom.
 
 
At first glance, it might just blend in and some might not even make the connection that it leads to the kitchen and those that do, may not make the connection that it is not connected.  What I mean here is that if you turn the vent fan on above you range and if it is blowing air out at you then it is a recirculating fan.  Why is this important?
 
Often times when a kitchen is remodeled little thought is given to the kitchen exhaust requirements.  Many times the connection with the preexisting fan is not used.  To further the trajedy of not reinstalling proper ventilation, nothing is done to seal and insulate the void leaving a large thermal bypass in a highly traveled area of the house.
 
Here are a few shots of the kitchen for some more perspective.
 
 
Missing microwave/exhaust fan in the location of the outside vent hood. 
The kitchen had exhaust at one time.
 
Notice the area above the stove top.  There is nothing there.  Earlier I mentioned that the homeowner just purchased the house so this is the situation they inherited.   The story for me was starting to take shape.  The kitchen at one time had working exhaust and during the kitchen remodel it was eliminated, but the end result is a big offender when it comes to why the kitchen is not comfortable. 
 
 
From the outside you can see that the depth of the exterior wall is roughly four inches and seeing the old wiring and the inside panel that this was a source of some of the problems in this kitchen.  Thermal imaging confirmed it.
 
 
So keep this in mind if your kitchen is cold and drafty.  It is possible this issue can exist if a microwave oven or range hood is in place with a new recirculating fan.  The old exhaust hood is a gateway to the outside as seen in this example. A clue would be to look outside to see if there are any vent hoods not associated with any appliance.
 
This is a sample of a remodeled kitchen in an older home that has a recirculating microwave above the stove.
 
So, how can you fix this yourself?
 
Here is how you do it.  Find something solid, easy to cut to size and air tight.  Sometimes heavy duty styrofoam furniture packaging will work.  Another option is a piece of polyiso insulation foamboard from the hardware store, but check to see if you can find something around the house since you don't need much.  Be sure to do the blocking part.  You don't want to shoot a bunch of foam insulation in the hole and muck it all up in case you need it later or stuff fiberglass insulation in there because that will not work.  Cut to size, place in the void and seal around the perimeter with spray foam.  This will insulate and air seal at the same time and fix the thermal bypass in that location.
 
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