What to Know Before Switching to Whole House Heat Pumps | Ask This Old House

[Music] hey Ross hey Kev going through the mailbag I'm answering carine's question she's in Arlington Mass and she asked about she has got an existing gas furnace and she wants to upgrade to heat pumps oh my gosh her and everybody else what's going on everyone wants that heat pump now I know a lot of questions a lot of rebates a lot of tax credits A lot of people it's the craze right now okay so what are you thinking about when it comes the heat pumps so the first thing is how a heat pump works right they are super efficient and they generate heat but it's low temperature heat meaning that if I'm sending hot air through this with the heat pump it might be 100° Supply Air leaving the heat pump and how does that compare to say a furnace or a boiler when there's a big flame in that machine yeah we might have 140 160 degree air coming off an oil or gas furnace right so with a heat pump we have to make sure we do our homework right to make sure that this system and all of those that are applied to it are sized correctly okay right so how do we go through that process yes so I'm working on a flowchart that really starts to understand what you know the questions to ask and how to map through it of course you are a flowart the first thing is climate zone right so if I'm in the southern part of the climate you know this is you know climate zones one through four yeah that's those are warmer climates those are cooling dominant so heating is really not as much of a need and then for the colder climates like 5 through eight like where Caroline is in 5A that area we're doing a little bit more homework to make sure that it's going to work right so when you say climate zones you're referring to I'm talking about the energy conservation code is a map of all the climate zones across the United States so what's next on your list next up is fuel source so if you look at you know historically electric baseboard has been the most expensive system to heat a building and followed up by your propane and oil furnaces would be your next and then gas and heat pumps are kind of there and the kind of the next category there and even if those prices have moved around has that order ranking stayed the same over the years just about yeah and so it's always very important to make sure that we are installing these heat pumps to lower the operating cost of that building so the more expensive like resistant electric the easier it is to knock them off and say yes this is a good idea that's right at at gas where it may be cheaper maybe not so much that's right y so it begs a question to go to the next one which is system type right so if I am a forced hot water system or if I'm a ducted system two different opportunities there forced hot water is base boards or radiators yep most of those houses are going with mini splits like your duck lless you know or ceiling cassette units because there is no duck work right and in that situation you haven't really replaced the baseboard you sort of supplement it that's right so we call those dual fuel hybrid systems right so they still have the ability to heat and cool through the heat pump but they have the ability to use the old existing heating system if they need to when it gets really cold out so let's talk about ducted systems like Caroline has how do we know if it makes sense to replace a heat pump into ducted system so the first thing I look at would be duck size meaning can the heat pump move the right amount of CFM the right amount of energy through the existing duck R so generally you'd want bigger if I understand this correctly because it's a lower temperature air you probably have to deliver more of that air than if it was a 165 degreee air 140 degre air that's right but we can use tools like this to measure right so we can actually measure the static pressure that's in the duck system kind of analogous to like blood pressure but for duck work to make sure that hey if my fan has to work really hard to move the delivered CFM the cubic feet per minute through that duck system if it have to work really hard the heat pump might not be able to work to be able to deliver the right amount of energy to that far bedroom at the end of The Wing So size is important and you can measure for that that's right the next one is leakage and making sure that it's insulated especially if this is running in an unconditioned attic right so if it's if it's big that's okay but if it's leaking air everywhere not so good that's right or if it's a million degrees or Zer degrees in the attic and not insulated it works that much hard think about all that 100 degree heat that the heat pump efficiently generated now it's leaking it to the attic and nobody wants to never gets to the room all right so you go through all those decision points you make a recommendation to the homeowner that's right is the homeowner ever in a position to do this on the own or just call up who's ever offering the incentives or they should they really always be getting somebody to help them with the calculation they really should be leaning on someone that does this every single day somebody that knows what they're doing that can do the testing to make sure that these heat pumps are designed and installed appropriately all right well listen it's a flowchart so it's a little dorky but I know it's going to help Caroline and a lot of other people too so thank you cool thanks for watching this old house has got a video for just about every Home Improvement project so be sure to check out the others and if you'd like what to see click on the Subscribe button make sure that you get our newest videos right in your feed

Channel: This Old House

Views: 33,466

Keywords: This Old House, Home Improvement, DIY, Construction, Ask This Old House, Building, heating, budget, Ross Trethewey, Kevin O'Connor

Id: 5wNfMHSI1Ug

Length: 4min 29sec (269 seconds)

Published: Mon Apr 08 2024