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My house currently is heated by a hot-water boiler, with radiators in the main rooms. The bedrooms have no radiators (it's an old house and I guess when it was built they figured the central radiators were enough, which they are if you leave the bedroom doors open a bit).

The boiler is nearing the end of its life and I'm wondering if there is any reason why I couldn't replace it with wall-mounted ventless gas heaters (like this, as an example only: https://www.homedepot.com/p/Dyna-Glo-30-000-BTU-Natural-Gas-Infrared-Natural-Gas-Wall-Heater-IR30NMDG-1/206556628). I'd make sure the total BTUs met the requirements of the space. (I'd also make sure my carbon monoxide detectors work, just in case, given that these are ventless.)

Would this create any code violations or other problems? It's common in my area for folks to install one or two of these in their houses as auxiliary heat, but I've never heard of anyone using them as their only heat source, so I'm curious.

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  • Investigate the cost difference between running a gasline to each heater and a hot/return pair waterline. Also that boiler is going to be feeding other hot water users so you'll still need a new one. Apr 12, 2019 at 14:59
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    "ventless" heaters require adequate room air ventilation - there's nothing magic about them them makes ventilation optional, it's just omitted from the appliance itself. Replacing the entire heating load with ventless heaters will very likely cause problems with adequate ventilation, unless the house leaks like a sieve - in which case, vented or sealed combustion heaters and tightening up the house will save a lot of heat you are/will be wasting on heated air leaks.
    – Ecnerwal
    Apr 12, 2019 at 15:27
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    Why are you so keen on wall-mounting ventless heaters, instead of sticking something in an exterior wall that vents to the outside? Also, yes, can you explain why you think that the boiler is reaching EOL, and why you don't want to invest in a replacement boiler, which is likely going to be more efficient than throwing wall heaters at the problem in this day and age? Apr 12, 2019 at 22:17

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If it were me I would investigate the ability to use the existing boiler to heat the entire house. You said that the boiler is reaching the end of it's useful life; please explain why you think so. Hot water boilers can last as many as 100 years. At that age they are not usually very efficient but they will still heat a home or building. With a useable boiler you have many options to extend the heating system into the unheated rooms. Using unvented heaters as you mentioned is not a good option. You will have the smell, the excess humidity, running new gas lines to each one, the depletion of breathable oxygen and other things to consider. I would never use one of those heaters in a confined space or room. They are cheap for a reason. Go find a good boiler guy and investigate your options using the old boiler. my 2 cents

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Whether ventless gas heaters are allowed by code in bedrooms appears to vary by state, this can be seen in the warnings and cautions section of the install manual for ventless gas heaters. Even if this is not a code violation then this might not be recommended by the manufacturer and so if installed in a manner not fitting with the recommendations the manufacturer may put up a fight if there's any cause to call for warranty repair and/or technical support.

In a similar issue on installing into bedrooms there may be problems with local codes and/or manufacturers if the ventless gas heater is used as a primary heat source. Using ventless gas heaters as the only or primary heat source could mean too much humidity and too little oxygen than is safe and/or comfortable.

Managing the oxygen issue would be done by ventilation to the outside. The installation manual will give recommendations but given this is likely a matter for a professional installation presumably the installer will perform the correct modifications as part of the installation to keep the house up to code. Ventilation will mitigate the humidity issue some but a dehumidifier may be needed. A side benefit to the dehumidifier is that it will add some heat as it takes humidity from the air, this heat is usually considered a downside as most people use dehumidifiers in summer.

What I expect a professional installer to recommend is putting electric heat in the bedrooms and bathrooms, with ventless gas heaters in the other spaces. This is perhaps a balance on managing safety and cost of electric heat (vs. what is usually much cheaper natural gas) without going through what might be far more extensive (and expensive) remodel of running new centralized heat.

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  • Could someone please explain down vote so I could improve my answer?
    – MacGuffin
    Aug 20, 2023 at 3:49

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