Heating a bonus room, separate from main heat

[Lucky C]

I have a 16' x 24' addition which is awkward to keep warm because of its size and location off to the side, but it would be nice to have it be heated in a cost effective way. Currently we just have an electric space heater which would be too costly to run regularly. I estimate that in winter it would take about 2000 W continuously to heat it electrically. Not gonna happen. However if we just want to heat it about 10F to 20F during the cool months, and don't care about using the room in the winter, we have a bunch of options.

1. Continue to use the space heater whenever we want to use the room. No up front cost or effort, but expensive per use.

2. Get a vent booster fan to blow in heat (via ductwork and oil heat). There is one small vent in the room but currently no hot air reaches it. Not sure how well a booster fan would work, with one vent for the whole large room?

3. There's a kerosene heater in the room from the previous owner that probably works, but I'm not sure if I even want to try it. I hear they are smelly?

4. Start a fire. There's a fireplace that even has fans built in to blow more hot air into the room, but it is still probably very inefficient.

5. Get a pellet stove and an insert to exhaust up the chimney. This is appealing if I'm going to be using the room on a regular basis, and pellets aren't too expensive right?

6. Solar hot water system, but just to transfer heat into the room, not to heat our water. The roof gets a lot of sun but the floor is on a slab, so if we can't do radiant heat then I don't know if there is a good way to get solar heat into the room.

What would you choose if you just wanted to heat one large room in Spring and Fall (in New England)? Occasional space heater use is OK for now, but I'm thinking I'd be using the room more often after I FIRE and would want a better solution than electric.

[Fish]

Rocket mass heater?
https://richsoil.com/rocket-stove-mass-heater.jsp

[Riggerjack]

1. Electrical heaters are 100% efficient.

2. As efficient as you oil heater. We almost never see oil heat on the west coast. Too spendy with oil competing against hydro.

3. Ick.

4. Blow your heated air into a fire to send up the chimney? Just as efficient as it sounds.

5. See 4, and add cost of pellets. You can duct in fresh combustion air, but it doesn't solve the efficiency problem. I have 2 pellet stove myself. I wouldn't recommend it.

6 solar and a radiator would be the optimum for efficiency, but not as convenient. Let me know what you decide for an antifreeze.

Honestly, in that situation, I would install a ductless heat pump. Go to Ingram for a DIY package, for price comparison. Fairly simple install, diy concrete and electrical. There may be some special tooling for coolant lines, or you can get a precharged system. I haven't done this yet, but this is how I plan to heat the garage I haven't built yet...

[Lucky C]

Electric heat is only 100% efficient within your house. A lot of efficiency is lost when generating the electricity and delivering it to your house!

But I agree with your assessment and will look into a basic heat pump. Also, a rocket mass heater would be neat.

There was actually a vent booster in the duct already, with its cord cut. It would need a relay to control it to turn it on only when the heat is on. However it wasn't doing anything when I wired it up and plugged it in - still couldn't feel any heat coming out of the vent. Removing it and sticking my hand in the vent made me realize that the air just isn't blowing as strong as it should down that branch of the ductwork, where there are a few ducts shoddily routed together. Which leads me to...

7. Rework the ductwork in the basement so that the heat actually flows into the bonus room. This would be ideal if it's possible and if we are going to be using the room more regularly. Oil is relatively cheap, for now!

[Riggerjack]

Oil furnaces burn hot. If their isn't warm when it gets there, first get some pooky and seal it up. Then think about insulating the ducts. How's your filter? Your fan?

[bryan]

If improving your insulation or airflow doesn't fix it and you don't want to do a fire, maybe a solar water heater that feeds into your hot water heater that goes to the bonus room that feeds into the solar heater might work (if you are a fan of control systems and building stuff)

[Riggerjack]

Yeah, pouring a radiant floor is possible...

But the slab isn't insulated, unless this addition was recent, and they wanted to spend more money insulating a slab in the room they apparently didn't plan to heat.

That means by the time you insulated, and pour a new slab, the floor is 6 inches higher. Even if the layout allowed easy transition, the lower ceilings are going to be very noticeable.

[bryan]

Wouldn't have to be a poured floor radiating, could put a radiator in the corner (with a fan)!

This is likely overkill (insulation followed with gas/diesel/wood heat if needed probably the cheapest/easiest) but sounds fun to me..

[Campitor]

• You could use an electric blanket to stay warm while you're in the room. Way cheaper than trying to heat the entire room.
• Do you have a southern facing wall available anywhere? You could hook up a solar powered pump to run a water/glycol solution to a heat sink within that room via some insulated hose. The hose would coil through an insulated box stationed at the southern facing wall where the sun would heat up the water and keep the pump going during the day when you're in that room.
• You could also cover the windows with a DIY insulated cover to stop any thermal bridging through the windows. If the slab isn't insulated, you could put a rigid foam layer down and cover it with a wall to wall rug to help retain heat; throw down some 1/2" plywood between the rug and the insulating foam if the floor feels too spongy.
• Keep a microwave in the room and heat a hot pack and stuff it in your pocket/shirt.
• Move your water heater to the spare room and let the pilot leech heat into the room as it burns throughout the day.
• Drop and do 50 burpees every 15 minutes - you'll stay warm and get a work out at the same time.
• Buy a snow suit and throw it on when in the spare room - you'll stay warm without the need for any powered appliance.
• Become a practitioner of the Wynn Hof method and laugh manically at everyone else that feels cold while in your spare room.
• PETA trigger warning - hunt down a grizzly and wrap yourself in its pelt while in the room - give a Tarzan like yell every time you put it on.
• Invite 10 of your best friends over - the body heat alone will warm up the room.
  A human gives off about the same heat as a 100 watt bulb per hour: http://www.physlink.com/education/askexperts/ae420.cfm
• Get an enclosed compost bin that vents to the outside and let the fermenting biomass warm the room.
• Move your Fridge into the spare room, the compressor will pump heat into the space. Bonus points when the room gets too cold - the fridge's compressor will stop cycling adding into $$$ savings.
• Take up ice sculpting part time - sell your creations and use the money to offset the bill of an electric heater or better yet just ice sculpt full time and forget about even needing to heat the room. Wins all around..

[Lucky C]

@bryan, @Riggerjack
Actually raising the floor and adding insulation is an interesting idea that I hadn't thought about. This weird bonus room is lower than the rest of the house, currently with awkward stairs and a floor that isn't completely level, and flooring that isn't great quality to begin with. The reason that it's at this lower level is that it lines up with the carport while also being only three steps down to the backyard. The ceilings are very high too. Not sure what's under the flooring, but if there's insulation there it's not thick, and is at least worth investigating. I think the main pain with adding insulation would be having to elevate doors and modify steps... so probably will be filed under "not worth it".

Nice ideas Campitor! It would be good to use as a workout room without turning on any heat. We will actually be having about 15 people in there for Thanksgiving, but I estimate that would only be barely enough to maintain "room temperature" in there (only will be a high of 40F on Thanksgiving). It's a big room with lots of areas with low R value. For Thanksgiving, preheating with a space heater will be fine, but I'm thinking potential future use as a homeschool classroom for the wife and kids. However we could just homeschool in the living room, and put the TV and video games in the cold bonus room to discourage excessive couch potatoness.

[Campitor]

Thanksgiving for 15 people? Have you considered covering the table in a tablecloth that drapes very close to the floor? You can put a heater with a thermostat under there which would contain the heat under the table which would keep the legs warm and keep the table warm. The Japanese do something similar: https://en.wikipedia.org/wiki/Kotatsu. Keeping the table warm will keep the hands warm and the heat under the table will keep the legs warm. We tend to feel cold in the extremities so keeping them warm will make your guest feel warm. Just a thought. Don't be afraid to cover the windows. Maybe heated seat cushions too? https://www.amazon.com/slp/chair-warmer/4m447xpkvg8x76t

[pk+]

Fixing air leaks seems to be easiest.

[vexed87]

Worry about insulating and draft proofing the room before cutting heating costs by switching heat source. This however only makes sense if the room will be used regularly.

Cheap options:
Caulk gaps along the floor/skirting and around window frames, weatherstrip the hell out of external doors and windows, insulate power sockets, cover windows with curtains/shutters after dark for next to no money.

Nuclear options:
If budget allows, double/triple glaze any existing single pane windows, get some professional roof, wall and floor insulation installed (in that order).

As others have said, space heating is inefficient, and you should first 'warm' the individual, not the space where at all possible. Wear jumpers and shoes/slippers to insulate your feet from colder floors, this will go a long way to making a cold room feel warmer. Seen as though you have a large group using the room as a one off, using a 2000W heater isn't a big deal if it's only one day, but if the room is utilised on a regular basis, the case for investing in insulating and improving heating efficiency increases drastically.

Also, whilst electric heating is technically 100% efficient at point of use, it's not an appropriate (in the context of sustainability) source of heat as it's woefully inefficient as losses from burning of fossil fuels to generate electricity is ludicrous. Conversion to electricity result in significant losses, and that's before transportation via the grid and back to heat again, usually only ~30% of the energy burnt at the power station is used to generate heat at the point of use for electrical heating, this is why those that can usually do burn natural gas in central heating systems, losses are much less and usually costs less than electricity by the kWh. Wood is a good alternative as biomass is renewable, therefore losses to the outside via flue shouldn't really come into it. Swap out the efficient wood burner for a rocket mass heater and vent it via a thermal mass object (stone or thermal bricks that retain heat) and you will ensure maximum heat transfer from the exhaust is captured before it escapes outside, heat will radiate back into the room well after wood fuel is spent.

Comparing efficiency of burning renewable biomass and venting to outside via a flue vs doing exactly the same at a power station, but then converting to electricity and back to heat again is obviously a no brainer in favour of wood. However, with wood you're less dependent on grid energy to keep warm in cases of outages... so there's that too. On the flip side, air quality in the home can be compromised when burning wood, particularly bad if you care about respiratory diseases, asthma etc, it will also affect your neighbours if you don't live in a rural setting (where air quality is less of a concern). Also consider if you have to source your wood via non-sustainable sources, (i.e. relies on petroleum for harvesting/distribution, I'd go with natural gas over electric to minimise total emissions). If you have the option to source willow from waste, or a sustainable coppice, I'd jump on wood as a heat source. No matter what anyone tells you, there's no such thing as burning fuels that dont cause greenhouse gas emissions, passive solar (water) heating is the only promising direction we can go to minimise total emissions and mitigate AGW. But passive solar is totally ineffectual during cold harsh winters unless your lucky enough to live in the sunbelt. So having a an alternative to fall back on is necessary evil. At least wood burning doesn't rely on grid/military industrial complex and is somewhat compatible with energy descent scenario as long as you can secure a source...

[Lucky C]

...
4. Blow your heated air into a fire to send up the chimney? Just as efficient as it sounds.

5. See 4, and add cost of pellets. You can duct in fresh combustion air, but it doesn't solve the efficiency problem. I have 2 pellet stove myself. I wouldn't recommend it.

Why don't you recommend pellet stoves, besides some heat being lost out the flue? Modern units are supposedly pretty efficient. Obviously you can't make one where all flue gases but no heat exit the exhaust, but they're designed to get as much heat blown into the living area as possible, unlike fireplaces.

I'm now thinking about getting a pellet stove for a primary heat source (still use oil but not as much) and to help with this unheated bonus room. I figure it could save something like 1/4 to 1/2 heating costs vs. our current system, while being more sustainable and reducing our sensitivity to oil prices.

They just seem great from what I've been reading so I'm interested in hearing about drawbacks.

[suomalainen]

Consider a masonry heater. You can order a core kit and then face it yourself I think.

https://mainewoodheat.com

[Riggerjack]

I own 2 Whitfield pellet stoves. They came with my first house, I have replaced nearly every component, between the two. Combustion fan, auger motor, auger bushings, distribution fan, vacuum sensor, control board, high and low limit switches. They are pretty simple to troubleshoot, but parts are unreasonable, and needed too often. BTW, the Whitfield is very popular for a pellet stove, in that you can get parts, many of them were made by companies that folded without parts support.

Pellets are messy. The dust, the ash, the chimney sweeping, none as bad as wood heat, but certainly the second dirtiest option. Pellets are made from a waste stream, but since pellet stove have come to market, we have found lots more uses for sawdust. Now sawdust is a product in itself, there is no environmental gain in diverting the sawdust into pellets, and the sawdust has enough value that pellets aren't very economical. With careful shopping, I generally pay around $220-240/ton before tax. Maybe cheaper than oil, but that's a low bar.

[Riggerjack]

Nuclear options:
If budget allows, double/triple glaze any existing single pane windows, get some professional roof, wall and floor insulation installed (in that order).

It's very easy to spend too much on Windows. The benefits of double pane are self evident, but the testing of windows for thermal efficiency is notoriously sales oriented. I would take U ratings with a fist sized grain of salt. Also, the U ratings is the inverse of the R rating. So a cheap vinyl double pane windows may have a U ratings of 0.33, and a very high end wood wrapped vinyl window with triple glazing and Noble gasses filling the spaces with a U rating of 0.22. The first is $200, and about R-3. The second is $2000 and about R4.5, if you believe the sales testing. Save the money, get thick curtains.

[vexed87]

Oh yes, agreed, but it depends what your starting point is, if you have a few small leaky sash windows, the change to a most basic correctly sealed single glazed window frame will provide perceptible difference in warmth and thermal efficiency. The fact that you have sealed drafts will be a bigger deal than adding any extra pains of glass. If you were building a house from scratch however, you'd might take whatever was most cost effective, but a room will often only be as warm as its weakest link. If you have more than a single small window frame, e.g. a sunroom which is pretty much floor to roof glass, you'll want to ensure you don't scrimp on the window construction, or the room will be unusable 6-8 months of the year north of 52nd parallel. Of course, sunrooms are not thermally efficient, but it illustrates the point. If energy efficiency is your primary concern, any windows that don't serve a function should be bricked up!

[Lucky C]

@Riggerjack well since all I have for heat now is oil or a space heater, oil is the much cheaper option vs. electric, so that's my baseline. Not only are pellets less expensive, but perhaps more importantly a good enough pellet stove could be had for $1k. Compare that to everything involved with buying and maintaining the furnace, oil tank, ductwork... I'm betting the average pellet stove would be dramatically cheaper to maintain vs. oil, plus I like that pellet stove maintenance is more DIY-friendly.

Also, it's a lot easier to clean up pellet dust than oil spills.

Thanks for the info, still seems like pellets would be a nice upgrade for my situation.

[Riggerjack]

Well, if you go with pellets, plan your chimney. Pipe is available online. I was surprised by both how expensive it was, and how hard it was to get a good deal. That was 10 years ago, so maybe you will have better luck.