--- title: "We Added an Additional 2 Bedrooms to Our 1968 House. Should We Buy a Bigger Furnace to Help Push The Air?" description: "An HVAC pro answers your real questions about heating your home this winter." date: "2024-11-06" modified: "2024-11-06" authors: - name: "BobVila.com Staff" link: "https://www.bobvila.com/authors/bob-vila-staff.md" url: "https://www.bobvila.com/interior/ask-a-pro-heating-adding-two-bedrooms/" categories: - "Heating" - "Heating & Cooling" - "Interior" tags: - "DIY" - "News" --- # We Added an Additional 2 Bedrooms to Our 1968 House. Should We Buy a Bigger Furnace to Help Push The Air? ![Professional fixing hvac system.]() *Photo: istockphoto.com* Welcome to Ask a Pro! We take your questions about home improvement, DIY, lawn and garden, and homeownership and answer them with the help of professionals. Our experts are vetted and verified—and they’re eager to share their knowledge. Last month, BobVila.com readers submitted home heating questions on Facebook and Instagram, and via our newsletter. We hand-picked our favorites, and tapped Micah Sherman of [Frontdoor]() to help answer them. In this installment of our Ask a Pro series, Micah tackles your questions about your home heating issues. He'll also be joining us for our [Ask a Pro LIVE webinar event about home heating for less money](). ## We added an additional two bedrooms to our 1968 house. Should we buy a bigger furnace to help push the air? —Frank, via Facebook **Micah's advice:** You have a lot of options here. Without knowing the exact size of your home, the rooms you added, or the size of your system, I can’t give you the “correct” answer for [what size furnace you need](). But there are some things you could consider when making your decision. First off, just increasing the size of your furnace won’t solve your issue without adjusting your ductwork as well. It doesn’t matter how big your furnace is, if your ductwork isn’t large enough to handle the amount of air that a larger system can push out, then there isn’t any value in increasing the size of your furnace. The right way to do this is to have a Manual J test performed on your home by a professional. This is a series of calculations performed on your home to determine the HVAC needs of your home - it will tell you the tonnage required to properly heat and cool your home. Any qualified HVAC technician should be capable of performing one of these tests. You could add some duct runs to those bedrooms, and that will bring air into those rooms. However, bear in mind that there is only so much air available to be used. Just like a pie, the more pieces you cut, the less there is per slice. So, the more air that we divide in your home, the less each room will get. Doing this may solve your issue, but it could also negatively affect every other room in the house. Another option would be installing ductless mini-split systems in those rooms. Doing this would remove the need to adjust the size of your furnace or ductwork, since each room would have its own mini-AC/Heat system. Many homes around the world use these, and they’ve gotten quite popular here in the United States as well. ## I'm 57 and I live in a 1955 Rambler-style home. Growing up I never heard of duct cleaning. However, I have seen ads for it over the past few years. Is it actually necessary, or is it just a way to make a buck? —Mike, via Facebook **Micah's advice:** Whether or not duct cleaning is necessary heavily depends on what type of ducts you have, how dirty they are, and whether they’ve ever been cleaned before. If you have a flexible duct or duct board, I [would not recommend having a duct cleaning]() performed. The risk of ripping or tearing the ducts themselves is relatively high, which would cause more problems. Also, duct board has a protective lining built into it, which keeps the fiberglass out of the air stream. If the tools used in the duct cleaning rips this liner, it exposes the fiberglass beneath it which allows it to enter your home. If the ductwork is dirty enough to warrant a duct cleaning, it may be worthwhile to consider replacing the ductwork altogether. You can clean these types of ducts, but there is risk involved. If you have metal ductwork, ensure that the company doing the duct cleaning has the right tools. When a proper duct cleaning is done, they will cut a hole into the supply and return to hook up the vacuums and will also brush the runs down towards the system. They will also have a vacuum truck as well, not a shop vac on wheels. If you’re having a duct cleaning performed, The [National Air Duct Cleaners Association (NADCA)]() recommends cleaning your air ducts every three to five years. However, I would recommend checking your ducts before getting them cleaned. Every 3 to 5 years is probably too frequent in my opinion. By keeping your HVAC system and home clean, you drastically reduce the need for duct cleaning. Routine maintenance on your HVAC system helps keep the air in your home clean, thus keeping the ducts clean. In the meantime, you can remove the air vents yourself and clean them, as well as the duct run as far as you can reach with a shop vac. The ducts are usually dirtiest near the vents anyway. ## What is the best way to insulate an existing crawl space? I know insulating it will help reduce heating bills but I don't want to have problems with moisture build-up and mold. —Shawne, via the newsletter **Micah's advice:** You’re right, having your home well insulated will definitely help reduce your heating bills. The best way to [seal a crawl space]() is to use a vapor barrier and spray foam. You want to avoid fiberglass insulation. The main goal here is to avoid moisture in your crawlspace—we want to do everything we can to avoid mold growth. Spray foam insulation and rigid foam insulation are highly resistant to moisture and can effectively seal gaps, which creates a barrier against humidity and air leaks, which is key to avoiding mold development. And always install a vapor barrier alongside the insulation to further prevent moisture. You also need to make sure the floor itself is dry. It doesn’t matter what you do, if there’s standing water, you’re in trouble. So before insulating the crawl space, remove any excess water, and then insulate. This might require adding a drain if you have water frequently seeping into your crawl space area.