I have completed over 1500 home energy audits in Maryland. BGE and Pepco standards require me to measure exhaust ventilation rates and determine where each exhaust fan in a residential house terminates. I am also required to manage new fan installs and air flow at the end of home performance projects in order to maintain proper indoor air quality. So, I am around this stuff every day.
Did you know that your bathroom exhaust fan is basically a pathway from inside your house to the outside? If it is not managed properly it can become a source of problems ranging from fogged mirrors and high indoor humidity in the summer to a drafty house in winter.
Finding the right guidance can be overwhelming.
In this article, I want to help you avoid several pitfalls that could come along with a replacement exhaust fan project.
You will get answers to the following questions:
---- What are the 5 most important bath exhaust fan details that will give you a good head start? ---- How can a bathroom exhaust fan waste energy? ---- Should your bathroom exhaust fan vent to the attic or outside? ---- How do you properly vent a new bathroom exhaust fan through the roof? ---- What bathroom exhaust fan model provides good performance?
5 Bath Fan Things You Need to Know
Do Bath Fans Actually Need Love?
Most exhaust fans installed in Maryland homes vent moisture directly into the attic
--This causes mold
--This accelerates the age of the roof
--This degrades existing insulation
Bathroom exhaust fan ducts running through an attic can "sweat" during a Maryland winter if not insulated properly
Different fan models exhaust different amounts of air per minute
If an exhaust fan is making noise, that does not mean it is working right
Incorrectly installed fans can act as gateways to the attic increasing BGE and Pepco energy bills
A bathroom exhaust fan is important for indoor air quality and should be installed correctly.
Bathroom Exhaust Fans are Major Energy Waste Offenders
Stack Effect - A Building Science Principle
The stack effect is a building science principle that basically says that your house acts like a chimney in the 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 hot 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 inside the building you live.
When the heat is on during cold days, the warmer air that you're paying for rises like the heat and smoke in the chimney. The smoke leaves at the opening at the top of the chimney and so does your precious warm air - at the ceilings below any unsealed attic space.
When I mention this to people during audits I can see the sparks in the brain saying, "Where is my air going? I don't see any holes in my ceiling. What do you mean sealed?"
For starters, the bathroom exhaust fan is a great example of a location where this happens.
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.
Take a look below at this diagram of a modern high performance ceiling mounted exhaust fan.
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 and the 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 IR photos shows a leaky damper. As a result, this exhaust fan is a liability and a big communication point between the attic and the inside of the house.
One tip that I can give you. I typically find that those that report really cold bathrooms in the winter typically have an issue with the damper so you don't need an expensive IR camera to figure this one out!
Is it Okay if Your Bathroom Exhaust Vents Directly Into the Attic?
Your Home is a System of Many Working Parts
The majority of the Maryland housing stock have bathrooms with exhaust fans installed that vent moisture directly into the attic.
As you can see in the photo below, leaving exhaust fans unchecked for long periods of time can lead to bigger problems related to sustainability.
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". The result is compromised roof sheathing.
If you are experiencing comfort problems in your home then addressing the ventilation could go a long way towards warmer winters and cooler summers.
For example, in summer extra humidity can build up inside your home when moisture from the shower is unable to escape due to a poorly performing exhaust fan. High humidity levels in summer lead to less comfort and the tendency to create the urge to lower the thermostat. Controlling humidity in summer can have a profound effect on your comfort and energy bill.
The extra humidity that gets injected into the already super heated attic ends up in most cases right back in the house creating a cycle that is not helping to improve the entire system within the house. So, the end result is less comfort and higher bills.
Properly venting bathroom exhaust fans to the "outdoors" is not a high cost improvement and there are a few different ways it can be done. TOP
Where is the Best Place to Vent a Bathroom Exhaust Fan?
3 Ways to "Term" a Bathroom Exhaust Fan Duct
1. Through the roof (best)
2. Through the gable wall (preferred over soffit)
3. Through the soffit overhang (least desired)
The way to evaluate which is best for your home is to consider the location of the fan and which option creates the shortest path with the least obstacles for the duct to take. Sometimes the style of house or the features in a house will require special techniques that will weigh into the decision. Cost effectiveness should also be factored into the overall decision.
Shorter duct lengths will help the fan pull the listed volume of air from the space. The shorter the duct run the more effective the fan will be. For longer duct runs that are unavoidable, it is recommended that flexible ducts are pulled nice and tight.
In many cases, the shortest point to the "outdoors" is through the roof.
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.
There are three steps in the process of venting a bathroom exhaust fan through the roof for the first time.
1. Drill a 4" diameter hole in the roof sheathing (plywood) from the attic with a drill and the proper hole cutter.
2. Get up on the roof, prep the area, remove the top layer of shingles for the new fitting, seal the new fitting in place with roofing cement, secure the roof jack and the shingles around the disturbed area.
3. Connect the fan to the fitting from inside the attic.
Watch how it is done in 2 minutes...
If venting your bathroom exhaust fan through the roof is not an option for some reason, then going through the exterior gable wall is the next best option.
Which Bathroom Exhaust Fan does Hometrust Recommend?
With So Many Fans Out There - Which One Should You Get?
Much like most other home improvement projects, there are many details that go into proper installation of a new bathroom exhaust fan. One important step is to seal around the fan once it has been installed. This will help to improve energy efficiency and comfort by making sure that gap around the fan does not allow air to flow between the bathroom and the attic.
Watch us air sealing a newly installed bathroom exhaust fan during a home performance project in Maryland.
Despite all of the installation nuances, at the end of the day it is important for the fan to remove the moisture effectively and efficiently. The Panasonic Whisperlite has several models that are up for the challenge. With a flawless installation, the fans can be adjusted to pull between 50-110 cfm (cubic feet per minute). The minimum recommended setting for a bathroom with a shower/tub is 50 cfm.
If the fan in your bathroom has been confirmed to be pulling air, but the mirror is still fogging up then it may be that the cfm is not high enough to get the job done.
Watch a properly installed and vented Panasonic Whisperlite get the job done in this Laurel, MD bathroom.
In addition to a fan that really gets out the moisture, our customers seem to get really excited when reporting that the Panasonic Whisperlite is much quieter than their previous bathroom exhaust fan.
Another advantage to the Panasonic Whisperlite is that it is versatile and works well with outside components like moisture sensors and third party switches.
Did you know bathroom exhaust fans can also be used to improve indoor air quality? With speciality switches and timers, properly installed exhaust fans not only make for a more healthy bathroom, but bath fans can also improve a Maryland home's overall indoor air quality.
FACT: The drafts that you feel around your home on a cold winter day have very little, if anything, to do with the windows.
And, despite this provable fact, thousands and thousands of Maryland homeowners are replacing windows in advance of the cold weather.
But, I have news for you. Getting your windows replaced will not solve your drafty house problem. There is a reason that there are thousands searching online each day for answers to "why are my new windows still drafty?".
Guess what! The answers to that question are the same as they are to the question:
Why are my old windows drafty?
What causes drafty windows?
In some cases, preventing drafty windows lies squarely with the person who last used the window.
The biggest issue I see is when the top and lower portions of the window (double hung style) are not properly aligned so the lock does not close and there is a "manufactured" gap caused by the last person to operate the window. Many don't realize that the top sash will slip down a bit and needs to be pushed up for the two components to properly connect and create a seal.
Another reason that windows get the blame for drafts around a house has to do with physics and the density of cold air compared to warm air. On an extremely cold day windows can present a feeling that they are leaking air. But, what is actually happening is they are radiating cold off of the glass.
This happens when the air inside is a balmy 73 degrees and the air outside is a chilly 30 degrees. The glass in the window is obviously the weakest link and it gets cold. When the cold radiates off the glass it dives down (cold air is more dense than warm air) and it gives the sensation that there is a cold breeze.
People always describe this issue by explaining how they held a candle or match and it was flickering or blew out from the draft.
To many people's surprise, I usually can prove their theories wrong with proper testing and analysis during a comprehensive home energy audit.
Drafty Windows Meaning
Understanding why windows feel drafty and being able to solve your issue might require hands on learning to really believe in the science.
After I show a homeowner that the windows are not the air leakage source with testing and an inspection I can easily then explain why windows are getting the blame.
REASON WINDOWS GET THE BLAME: when a house has holes to the outside in the wrong places, which is typically the case, the windows will always seem much worse because the root issue is that the house literally has a conveyor belt of cold air infiltrating in other places that cannot be seen, but do exist.
Just about every single energy audit that I have done where the homeowner was convinced that the windows were the source of their discomfort we were able to uncover other issues around the home that proved to be the real reasons for the problem.
Who Fixes Drafty Windows
When a child has a cold there are two options for treatment. Cough medicine can be purchased over the counter by Mom or Dad and this will treat the symptoms - lessen the cough, lessen the runny nose, lessen the fever, etc.
A doctor, on the other hand, will prescribe antibiotics to get to the source of the problem and kill the infection.
Drafty windows are symptoms of the larger issue. A window salesman is the the grocery store clerk selling you the cough medicine.
Getting your home inspected by a certified home energy auditor is like getting the doctor involved. The auditor is going to point you to the source of the problem.
Drafty windows are solved by taking a whole house approach and considering the entire building envelope, not just the parts you can see through or walk through (doors).
How Do We Fix Drafty Windows
Drafty window solutions are not quite as obvious as it seems.
When you attack the areas of the house that are most susceptible to losing heating and cooling with the right materials and knowledge, the pressure dynamic in your home will actually change. The HVAC system that once could not keep up will seem like new. Cold window glass will not be an issue because the house is more comfortable and efficient all the way around.
So, the way we would fix your drafty windows is by sealing up areas in the basement and in the attic. Since warm air rises, we want to seal up the top so it does not have a place to escape into unwanted places like the attic. When warm air rising is allowed to escape unchecked, cold air streams in from the lower points in the house due to physics and positive/ negative pressure flow.
By using proper air sealing techniques, we can disrupt the pressure dynamic in the house and stop the warm air from escaping so it serves you much better and as a result the the house feels much cozier because all of the systems are working much better together.
Next Steps
Get a home energy audit & get questions answered such as:
Should I use blown-in insulation or rolled insulation? How much insulation do I need in my attic? How do I properly vent my crawl space? Should I remove old insulation from my attic? What is the best way to seal my crawl space? Is spray foam insulation the best solution for my home? Why are my new windows feeling drafty? Should I insulate the walls in my home? What areas should I seal to reduce drafts?
I have completed over 1500 home energy audits in Maryland.
If you just bought a home - congrats!
Chances are very high that you got a home inspection during the process and it has a list of things you need to do to keep it up to "code".
But, I am willing to bet that the list is missing many important things that can make your home super cozy and more energy efficient.
In fact, the false sense of security that most get from a good home inspection report can lead to years of spending money on wasted energy.
And all you get for all that extra spending is less overall comfort.
Talk about a LOSE/ LOSE situation...
Here are 5 reasons to get a $100 BGE or Pepco energy audit if you just purchased your home.
1. Turn it to a WIN/WIN!
Making an early comittment to the Home Performance with ENERGY STAR® program can often times lead to a project that pays for itself!
This table was taken from a recent Pepco energy audit report. The program for BGE and Pepco is virtually the same.
The family had been living in the home for twenty years at the time of the energy audit (since 2001).
They decided to get the work done and the cost of their air sealing and insulation project was $1538.64 after Pepco incentives were applied.
Annual projected savings are modeled at $197 per year making it an 8 year payback in energy savings (with added comfort as an extra benefit!).
This scenario makes it clear that getting a comprehensive energy audit as soon as possible can really save you money.
For twenty years this family was allowing roughly $158 of energy to escape their home unchecked.
Total losses at the end of twenty years: roughly $3170.00!
And, you can't even put a price tag on the better comfort they missed out on!
2. Find, Correct and Seal Connections to the Outside
Most houses have connections to the outside that are obvious and there are some that are not so obvious. These "pathways" are also reasons for high humidity in a home and unwanted pests.
An energy audit, unlike a home inspection, will test your new home's "shell" using a blower door test or pressure test. With the use of a large industrial fan, we can detect the leakage in a house and seal problem areas up so the house is less humid in summer and drafty in winter making it much more efficient. And, since bugs take the same pathways air takes, you will experience less pests as well.
Moisture problems in a house can take many forms. Most home inspectors will not be able to detect potential problems with poorly sealed or incorrectly insulated ducts which can sweat and cause drywall or hidden mold issues. An energy audit will evaluate all of these possibilities so you can get a handle on things early on.
Most homeowners, old and new, are surprised to learn during an energy audit that their home's exhaust fans are not functioning properly. I find that most times they vent directly into the attic area which can increase the chance for moisture issues throughout the home.
It is really hard to assess the fan with no tools. Exhaust fans around moisture sources that do not function properly will lead to higher overall indoor humidity levels.
A properly vented and working exhaust fan goes a long way towards sustainability. Your ceiling will not peel or turn colors if the moisture is properly exhausted.
3. Get the Real Info You Need About Your Insulation
This brand new home is short on insulation (R32) and passed inspections. In Maryland it is recommended that flat attics are insulated to R49.
The point here is simple. Most home inspectors see the pink stuff in the places they know it is supposed to go and they check the "yes" box on the form and move on to the next task.
But, old insulation techniques were not the best and all insulation projects require attention to detail. For example, if insulation is not in perfect contact with the surface of the wall or ceiling then it is not working nearly as effectively. This detail is not a requirement in a home inspection report.
Getting an energy audit in the beginning of owning a home is a good idea so that you can get a firm grasp on your insulation early. You will be able to rest easy as the seasons change and life is coming at you. The energy audit reports give you a clear snapshot of where your insulation stands now.
Are you well insulated? Moderately insulated? Poorly insulated? Eliminate stress - know for sure.
You don't have to get any work done right away, but you can make educated decisions about which areas need attention first. It is good to know exactly what is going on in those out of sight - out of mind areas of your home like the attic and crawl space.
4. Unbiased Feedback About Your Newly Inherited HVAC System
If you have read any of my articles there is one thing I say over and over...
You cannot put a new HVAC system into a leaky house and expect better results.
Air will continue to take the same pathways whether the system is top of the line and new or if it is twenty five years old.
Just because it looks terrible does not mean it needs to be replaced.
Getting an energy audit after buying a new home can really help you to prioritize projects. An energy audit will help you see your house as a sum of all of its parts and it will help teach you how they all must work together in order to give you back the least costly maximized amount of healthy comfort.
You will know exactly where you stand. Has there been any work done to the areas that need it in the past? How old is the HVAC? What size is the HVAC and is it appropriate for the volume of the house? What shape are the ducts in? Which opportunities for improvements exist and which will give you a maximized return on your investment?
There is no doubt the HVAC system in a house deserves special treatment, but don't make the mistake of rushing to buy a new system to improve any aspect of comfort inside the home unless certain other measures have been taken first.
5. Get an Early Check on Your Indoor Air Quality
Indoor air quality is commonly misunderstood as a number calculated in particles. Instead, it refers to getting fresh air into a home.
A BGE or Pepco energy audit is a great way to determine what your indoor air quality "score" is and how to fix any deficits that may exist. A great way to figure out indoor air quality is to consider a common misconception.
A very good carpenter that works around houses every day once said to me during a discussion about air sealing a house:
"Don't you need to let the house breathe?"
This comment has a direct tie to indoor air quality. The answer is, YES, of course. But, what we need to discuss is the difference between uncontrolled and controlled "breathing".
With the use of sophisticated modeling software, data collected during the audit will calculate the required air changes per hour for each individual home that is inspected. The assessment looks to tighten a building's shell, therefore calculations are made as the house stands now and projections are calculated if the house is tightened.
The great thing about the BGE energy audit is that you can find out your indoor air quality status now without getting any additional work done. Some houses are too tight before any measures are taken and the occupants are happy to know there is a deficit and how to remedy the issue. An energy audit consistently delivers the options for solutions which gives the homeowner complete control.
Next Steps
Get a home energy audit & get questions answered such as:
Should I use blown-in insulation or rolled insulation? How much insulation do I need in my attic? How do I properly vent my crawl space? Should I remove old insulation from my attic? What is the best way to seal my crawl space? Is spray foam insulation the best solution for my home? Why are my new windows feeling drafty? Should I insulate the walls in my home? What areas should I seal to reduce drafts?
As an energy auditor there is a lot of repetition to what I do. I see the same issues over and over again.
This is great for Maryland BGE and Pepco customers that need help finding ways to improve comfort around their home.
Here are five things you can do around a home that will make it more cozy in the winter.
1. Seal Recessed Light Fixtures
The first thing you can do to save energy at home and reduce drafts is seal up you recessed lights in ceilings that are below the attic. These common fixtures are secret gateways to the attic and there is no doubt your warm, conditioned air is sneaking right out.
Most older recessed lights have ventilation holes so that heat from the old incandescent bulbs can escape.
Pepco and BGE customers with recessed lights typically have some of the biggest bills and comfort complaints.
The photo above is taken from inside an attic. The flash on the camera was turned off to demonstrate the ability in some cases to actually see to the living space below. This is why all recessed lights must be covered and sealed at the attic floor to reduct drafts and energy loss.
A recessed light as seen from inside of the house.
Watch how leaky these recessed lights are during a whole house pressure test.
How Should it Look?
It is always best to seal recessed lights from the attic. Covering the fixure and sealing the cover at the base is key. Now the air barrier is restored and the home will be less drafty.
When sealing recessed lights from the attic is not possible, you can seal your recessed lights from the inside with an LED recessed light kit.
2. Seal Attic Floor Cracks, Holes and Gaps
Similar to the recessed light problem, there are other holes and cracks in the attic floor that will lead to the communication of air between the inside of the home and the attic, or outside.
Take your light switch on the wall as an example.
Wires run through the walls to hook up to electrical outlets and switches creating pathways for air to connect between the inside and outside (attic).
Foam sealant can be purchased at the hardware store and it can be applied to the tops of walls, around light fixtures and to seal up holes drilled for electrical wires. All of these voids contribute to a high bill and uncomfortable living space.
Watch how we do this!
3. Seal Accessible Leaky HVAC Ducts
Improving home comfort can be achieved when you put resources in the right place.
According to the EPA and other studies, the HVAC ducts in your home can be leaky enough to account for up to as much as 30% of a household's total energy loss.
Sealing ducts is not something that needs to be done by a contractor.
This is a "weekend warrior" type of project that requires a little patience, a few materials and a little know how. Sealing ducts near the air handler will also help you the most and those are usually the places that are most accessible.
Disconnected ducts are big energy wasters!
One way to fix leaky ducts is to use two-part spray foam.
Sealing ducts with mastic is another option to improve your home comfort.
4. Seal and Insulate the Attic Hatch
If you want to save energy at home and improve comfort, be sure to think about all of the places that you have access to an attic around your house. It is important to treat all of them.
Typically, the attic access points around a house are made from 1/4" plywood or drywall. This is no way to separate the inside of your home from the attic (outside). A few pieces of insulation and a 10' piece of weatherstripping can go a long way!
Thermography of the hatch in this home shows that the area is problematic.
Watch how a push up attic hatch gets treated.
5. Install a Chimney Balloon
If you have a fireplace, then you have another great way to improve your home comfort.
Most people keep the damper closed when the fireplace is not in use, but usually it is made of metal. Chances are there is nothing stopping the flow of air through the chimney damper flap and out. Using a very simple blow up type device can really help to move the needle and decrease energy usage and improve comfort.
A great way to save energy at home and improve comfort is to seal the chimney with an attic balloon.
The attic ballon has a stem that can easily be accessed to blow up the device and create a nice seal in the chimney.
Conclusion
Looking for these five things around your home and resolving one or two of them can go a long way towards better comfort and having a lower energy bill.
________________
Written by Eric Gans I have over 1000 energy audits under my belt in Maryland. I like to take my personal experiences with each of my audit customers and try to get the things that concern them out into the world so others can make good home improvement decisions - in the right order - according to their needs.
Did these ideas help you save energy at home? We want to know if you tried any of our solutions and how they worked out for you in the comments below!
Did you know that when you participate in a Home Performance with ENERGY STAR® project that the results are actually measurable?
Learn how getting an energy audit through the program uses a special air leakage test to determine where your home leaks the most!
Is there any other home improvement project that when it is all said and done you can actually test and get immediate, unbiased results?
I can't think of any!
Maryland Replacement Windows
Let's take Maryland replacement windows as an example.
Often times windows are replaced around a Maryland home to improve comfort and reduce drafts. But, results are typically subjective and more times than not there is a walk away feeling for both the homeowner and contractor that the windows did not really perform, but there is not much anyone can do at that point.
What is Home Performance?
Home performance work on the other hand is principled in science, proven by testing and solved by targeting the right areas of the home that leak the most.
ANALOGY: If a jet is not able to take off from the runway, do you want the airline company mechanic to just fix a perceived issue and give it a whirl, or would you rather the technician employ diagnostic tools, real time onboard computer information and proper calculations to get the plane back in the air?
Of course we all want the more informed approach to ensure our safe return to flight. The same should be said for solving complex home comfort issues.
So how does this work in home performance you ask? How can we be sure to target the right connections to the outside in a home so that we can get the results we want?
The blower door test!
The blower door test is an air leakage test - for your whole home, not just a door.
A great benefit of a blower door test is that the homeowner and the contractor can walk around together and physically inspect the house while the test is running to discover the leakage points in a physical sense - rather than in a hypothetical sense.
Participation in the air leakage test can have a profound effect. Seeing air flowing through areas of the house that you would not have ever thought can empower you to make good replacement window choices in Maryland.
Watch the blower door test reveal how leaky this light fixture happens to be...
How We Reduced this Home's Air Leakage by 30% - Not a Single Window Was Replaced
One great example of a home that made huge gains in comfort, reduced drafts and overall energy usage was a home in which not a single window was replaced. The results from the air leakage test were huge and the customer noticed a difference the first day.
Here are the blower door results as seen on the gauge used to measure the home's air leakage. Notice the number on the right from 4318 cubic feet per minute down to 3049 cubic feet per minute.
The results show a roughly 30% reduction in the leakage of this home.
This means that actual holes in the home's shell were proper sealed and the results have been measured through diagnostic testing.
So, what did we do to treat this house and make huge gains on reducing air leakage you ask?
Hometrust Remodeling's mission is to help Maryland homeowners create a more comfortable home and save energy by using building science principles and modern air sealing and insulation techniques.
An Energy Auditor's Purpose "Energy auditors visit residential buildings and talk to owners and residents. They inspect, test, and measure to decide what energy-efficient retrofits are practical and cost effective." Residential Energy
The stack effect is a building science principle that basically says that your house acts like a chimney in the 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 hot smoke rises and billows out of the opening at the top (positive pressure). 
REASON WINDOWS GET THE BLAME: when a house has holes to the outside in the wrong places, which is typically the case, the windows will always seem much worse because the root issue is that the house literally has a conveyor belt of cold air infiltrating in other places that cannot be seen, but do exist.
Drafty window solutions are not quite as obvious as it seems.
