Tag Archives for " HVAC "

Our Top Articles for Reference by Topic

Our Top Articles for Reference by Topic

We have published a lot of information for you on our website, so we understand it can be a lot to digest!  Here’s a shortlist of our top articles 

Mold and Mycotoxins

Mold Prevention

Mold Testing


Air Filtration


New Home Search


Home Projects for Better Air Quality


Disaster/Emergency Preparation

Sealing Air Channels in Your Attic

Sealing Air Channels in Your Attic

Anytime there is a significant temperature difference between the inside and outside of your home, good air-sealing and insulation will pay dividends in energy savings, air quality and avoiding damage to your home.  If you don’t understand what an attic bypass is, this video gives a number of great examples.  The host discourages homeowners from doing their own air sealing, but the fact is that not all states require attics to be air sealed before adding insulation to the attic (unlike Minnesota).  Therefore, you may be hard-pressed to find a contractor in your area who is knowledgeable about doing this.  However, if you are physically agile and willing to put in some time and effort, it’s achievable!  

The best times to get up there and tackle air sealing in your attic is during a swing season when you’re not using your heater or air conditioner (it’s a comfortable temperature in the attic).  Also, do it BEFORE adding any more insulation (you don’t want to be digging through your new insulation to find these gaps!)

Don’t forget to dress appropriately!  You’ll need:

  • Old clothes that can be laundered or thrown away, and a hat
  • Vinyl gloves to keep the sprayfoam off your hands (it’s sticky and stains!)
  • A headlamp if there’s not adequate lighting everywhere 
  • A respirator to prevent inhalation of fiberglass and dust (it’s good to keep extra cartridges on hand)
  • Safety glasses (because spray foam gets everywhere, trust me!) 
  • Knee pads (because low attics require a lot of crawling!)
  • Seal your cellphone in a ziploc plastic bag if you bring it with you (because spray foam gets everywhere, trust me!)

Here are some typical areas you will want to address:

Sealing Duct Shafts

According to Building America, a government program for testing and education about energy-efficient homebuilding, the proper way to seal duct shafts involves cutting a piece of plywood, rigid foam, or drywall to fit around the ducts, applying a bead of sealant like caulk to the supporting surface, fitting and securing the board with screws or nails, and applying more sealant around the inner and outer edges.  This is a great idea, except that caulk doesn’t usually cut it.  With the advent of spray foam in a can, it’s easier to get a good seal with spray foam than with caulk because the foam continues to expand for some time and will fill any voids.  

To seal gaps in and around ductwork, this video is great.  It shows several different types of repairs.  If you’re a novice, it might seem like you could just use “duct tape” on ducts, right?  Wrong!  Regular duct tape does not work well long-term on HVAC ducts.  It does not form an air-tight seal and over time, dries out and disintegrates.  That’s why you’ll want to use the following sealants instead:

  • Using Air Duct Sealant (paste, also called mastic) and fiberglass tape or fiberglass cloth to patch small holes and larger gaps in ductwork (for a small kit, check here)
  • Using spray foam to seal around ducts where they penetrate walls or unconditioned space like the attic or crawlspace.  There are different formulations in spray foam:
  • Use foil tape to seal around loose ends of insulation.  If there are any leaks in the ductwork, this will minimize air leakage in/out of the duct.  
  • Check out our article on sealing your registers: you’ll want to do this to prevent condensation on the grilles and registers in your rooms!

I had an idea that my attic was leaky; I just didn’t know the extent of it until renovating for a new HVAC system.  I found a shaft used to hold ductwork that was open to the attic, but plunged down one floor and shared a wall with my bedroom.  This air space channeled hot/cold dusty air from my unconditioned attic right down the wall and it was NOT insulated.  

Because the shaft was rectangular and housed 2 round ducts in it, I decided to stuff some loose fiberglass around the ducts at the top and spray foam over them; the fiberglass only acted to plug large gaps and keep the foam from falling down the shaft before it hardened.  The only thing to remember is that the foam must contact solid surfaces, like foil-covered insulation, wood, or foam board, in order to make a continuous seal.  If I had left loose fiberglass sticking up out of the shaft, the air could pass right through it. 

Insulating Electrical Boxes and Can Lights

Here is something I’ve been wondering about for quite a while.  I have a number of electrical boxes for ceiling fans, lights and even the bathroom vent which are not sealed.  What kind of sealant should I use?  According to this short video (with happy music) by the EPA, spray foam comes to the rescue again!  As long as your fixture box doesn’t generate heat, you are fine with spray foam.  This brings us to can lights.  Foam and insulation must not come into contact with older style can lights (which use incandescent, halogen or another heat-generating bulb) because of fire risk.  In this case, you’ll want to purchase a can light cover with fire rating specs in order to safely insulate the area around the light.  It can be sealed with spray foam around the bottom perimeter of the cover to the sheetrock.  Again, you do not want to let the spray foam contact any part of the can light, which can get very hot, so be sure to hold it down to the sheetrock when spraying, and minimize any holes necessary to accomodate electrical wires going to the light.  

It’s also recommended to plug holes drilled for electrical wires through the top plates of your walls (typically these are wood 2x4’s or 2x6’s).  If your local code requires that these penetrations be sealed with a fire retardant sprayfoam, then Great Stuff Fireblock with smart dispenser ($10) will work. 

If you want to keep your heating and air conditioning system working well, prevent mold and moisture damage, lower humidity in your home as well as lower energy costs, tackling air sealing in your attic is a must!

Photo by Will Francis on Unsplash

These steps convert your HVAC into a whole house filter

These steps convert your HVAC into a whole house filter

Many people have central air conditioning/heating, yet they don’t know that this machine could be used year round to improve the air quality in their homes.  For such an expensive investment, it’s wise to get the most out of it–everyday!  Here are a number of tips to do just that.

  1. Air-seal the return ductwork.  We’ve written extensively on air-sealing your home, attached garage and attic, but the return ductwork is super-important too.  A lot of contractors use wood or drywall to “frame” a duct but without sealing the corners, you are pulling dusty air from wall cavities, the attic and maybe even under your house, if the return air grille is near the floor.  Here is a great video on what to do and which products to use.  Air-sealing your ductwork is not a bad idea, either.

  1. Make air filter changes top priority!

If you’ve finally gotten on a schedule of changing your HVAC filter, we applaud you!  You are protecting this expensive equipment by preventing an overly-dirty filter from damaging the fan or other components, because dirty filters increase the pressure drop, like trying to suck a Big Gulp through a coffee stirrer.  Try to use a higher MERV filter (like 11, 12 or 13), first by reading our article How can I get more filtration with my current HVAC system, then increasing the MERV if you have enough filter surface area.

  1. Seal the filter in place.

There are several ways to make sure that air is not bypassing the filter.  

  • This video shows how to seal a vent grille to the drywall using spray foam.  Although this can also be done from the attic (with less chance of dripping messy foam in your house, not all vents can be accessed from above.  

  • For the return grille: caulk the filter grille to the drywall.  

  • Use filter-sealing tape over the filter:  

    • AllergyZone FilterLock Filter Slot Seal, $10, has a magnetic closure to stick securely to your filter slot opening, sealing gaps to maximize filter use.  The video on this page for the product shows how easy it is to install.

    • Or, if you have a filter that lies flat in a filter grille, use masking tape or painter's tape to seal the edges of it to the filter grille like in this video (I prefer painter's tape because it removes more cleanly). 

  1. If you have a BP-2400 Whole Home Ionizer, install it between the return air filter and evaporator coil, or before the fan, in order to get those ions circulating through your whole home.  Once a year, it helps to de-energize the ionizer and clean of any dust from the brush heads, which will maximize its efficiency.

  1. Set the fan to “on”, not auto.  This ensures that the fan is always running even if the heat or AC is not on.  If you’re concerned about the cost of running the fan all year, you don’t have to be.  Check out our article on how to calculate this cost to see that it’s not a lot (~$10 per month or less), especially for the reward of cleaner home air.  The bonus is that circulating air with this fan redistributes air throughout your home, reducing moisture content in soft furnishings and mold growth.

You are ready to go!  Dust, cleaning and personal products, pets, cooking–they all contribute to less-than-stellar indoor air quality, so it’s wise to make the most of what you already have to improve it!

Photo by Tekton on Unsplash