Professional Tips for Installing Ductwork in the Attic Above an In-Law Suite

One of my favorite things about Northern California is our beautiful historic homes. All over Sacramento, we have classic houses built many decades ago, some of which are almost 100 years old. In other cities like Roseville, Folsom, and Elk Grove, we have neighborhoods that sprung up in the 40s and 50s, bringing classic architecture to our region. There’s a lesson to be learned here about honoring the past, which I think also applies to something else I’m seeing all over our area these days: the addition of an in-law suite to local homes.

Now, in-law suite is the term used for rooms, garages, or sheds that homeowners have converted into bedrooms or small apartments. Whoever named them was probably building one for his mother or father-in-law, but homeowners in Northern California nowadays build them for all sorts of family and friends who come and go.

Regardless of who’s staying there, these spaces must have a comfortable heating and cooling system, and a key to that is quality ductwork. Every homeowner should know a few professional tips for installing ductwork in the attic above an in-law suite. Converting a room for a friend or family member to call home is a nice way to show them love—and making sure the temperature stays ideal is even nicer.

Installing Ductwork in the Attic: What to Know Before You Begin

installing ductwork in attic above in-law suiteOne of the most important tips for installing ductwork in the attic above an in-law suite is actually one for before you even begin the installation process. I’m talking about ensuring that the attic is properly sealed and insulated. I’ve brought up before how you can maximize AC efficiency and lower energy bills using attic insulation, and the same applies to the attic space above an in-law suite.

Roofing materials absorb the sun, especially metal sheeting or shingles made from asphalt, transferring heat through these surfaces into the wooden beams in your attic. The attic then becomes superheated, which in turn heats up the ductwork—and the cooled air passing through it headed for your in-law suite. Basically, you can have the highest quality, professionally installed vents, but if the attic is improperly sealed, the quality of the ducts won’t matter, making cooling or heating your in-law suite far more difficult—and costly—than it has to be.

Why Installing Ductwork in the Attic Above an In-Law Suite Is Necessary

Ductwork is necessary for an in-law suite because without it there’s no way for the air that’s warmed or cooled by your furnace or air conditioner to reach that space. The ducts are the veins of the HVAC system, circulating air throughout a house. You would think that every room in your home already has sufficient ductwork, but, unfortunately, this isn’t always the case.

Spaces such as back rooms, sunrooms, and porches, which I see homeowners convert to in-law suites all the time, don’t always have sufficient ductwork. In fact, sometimes they don’t have ductwork at all. This was fine when they were spaces only getting occasional use, but if you’re going to have someone sleeping there and calling it home, you’re going to need ductwork that connects it to the HVAC system.

How to Properly Install Ductwork in an Attic

Once your attic is properly sealed and insulated, you’ll want to focus on the proper way to install ductwork above your in-law suite. Here are some basic tips to follow:

  • Tip #1: Choose properly sized ducts. One of the most common mistakes when installing attic ductwork is choosing undersized ducts, which means not getting ducts large enough for the connected HVAC system. A number of problems result from this including noise, unbalanced ducts, and too much pressure. Unbalanced ducts mean that air is not flowing evenly through your system (resulting in some rooms being much warmer or cooler than others) while too much pressure means that airflow throughout your house will get worse—and less cooled air will be coming from your vents. My suggestion is to call an experienced HVAC pro to make sure you’re choosing the right size for your new ducts.
  • Tip #2: Give your ducts the proper support. This is an especially relevant tip for flex ducts (more on that in a minute), but you need to make sure any ducts in your attic have proper support. Hard ducts without proper mooring will be unbalanced—and unbalanced ductwork might be to blame for a number of HVAC problems. Improperly supported flex ducts will sag, which cuts down on airflow, meaning cool air generated by an AC unit will struggle to reach your in-law suite. Again, I’d suggest calling an experienced HVAC pro to guarantee your ducts are installed in your attic with proper support.

Choosing the Right Ductwork for Installing in Your Attic

As with home architecture and decor, there are trends in the HVAC world. For example, ducts fall into two types: hard ducts and flexible ducts. If I look in the walls of a home built before the 1970s, I can all but guarantee I’ll find hard ducts. If I do the same for houses built between 1970 and the mid-2000s, I’ll probably find flex ones. Newer homes are somewhat of a toss up. Basically, the trend was to use flex ducts after they were invented around 1970, which lasted until just recently when builders began to shift back to hard options.

Hard ducts are the boxy metal type you’ve probably seen secret agents crawl through in movies (except in private homes they’re rarely that large). Flex ducts, on the other hand, are smaller and tube-shaped, like giant shiny worms. They both have advantages and disadvantages; the right choice in ductwork for you likely depends on the specifics of the attic above your in-law suite. Here are some advantages for each:

  • Hard ductwork: This type of duct means a smoother interior with better air flow, insulation applied on the outside to cut down on fibers getting into the system, and a durable shell not easily punctured by rodents or UV light.
  • Flexible ductwork: These ducts are more cost effective, good for tricky installations in tight places where rigid ducts can’t fit, and ribbed coils inside the tubing do a better job ensuring the ducts are air tight.

Even with these professional tips for installing ductwork in your attic, you may still be unsure which is right for the space above your in-law suite. That’s okay. An experienced HVAC pro can pinpoint the duct setup that’s right for your home.

Installing ducts is a tricky business because they need to be installed as close to perfect as humanly possible in order to guarantee maximum efficiency. There’s a large margin of error, from insulation, sizing, support, or the type of duct you choose. But ductwork is key to ensuring your HVAC works properly, just like an HVAC is key to creating a comfortable in-law suite. Have an HVAC pro guarantee the space you’re building for your loved ones is one they’ll enjoy and be proud to call home.

Don’t take chances with the ductwork in the attic above your in-law suite. The trained professionals at Bell Brothers can guarantee you make all the right choices.

Image courtesy Unsplash user Ali Inay