Complex Heating Solution Needed?- (with diagrams)

[histguy]

Hello gang,

Have been reading posts on this board for a year or two now, finally time to ask everyone for their advice and opinions on my heating issue.

Quick Background

Bought this house last summer. Has a awesome 24x32 detached garage (See pic below) I live on the Keweenaw Peninsula in the UP of Michigan. Below zero temps are not uncommon, but also do not last for long stretches. Common temp around 15-20 from Dec-March. We do get 200-300 inches of snow every winter (only 119 so far this year). Summer is never over 75- so A/C is never needed.

Fuel Options

I do not have natural gas. Run propane and wood pellets to heat the house.
We have the 2nd highest electrical costs in the country up here (currently $0.24/KWH) and will be rising again soon. So electrical is not a long term option.


Garage Details

Garage is insulated with R-19 batting on the first floor. R-19 in the walls and ceiling of the upstairs rooms. 8 inches of cellulose is blown in between the 1st and 2nd floor in the 5 foot wide attic area on both sides of the upstairs rooms (in essence, unconditioned storage space).

Diagram of the 1st floor:

Diagram of the 2nd floor:

My Questions

My primary interest is to heat this upstairs room. It will be my ham radio shack. I want to be able to keep it at a constant 45 degrees during the winter and will be up there 2-3 days a week for a few hours each day, and occasionally for full days on the weekends.

I also however want to heat the downstairs main garage area to a level that makes it comfortable to work on the cars etc. Say 45-50 degrees. Would be nice to keep it at 35 degrees all winter, but not a necessity. Right now with no heat it rarely gets below 25 in there- and that is only when it is below 0 outside.

How best to go about this?? Do I need two systems? Dothey make a propane heater that I can hang downstairs and run a duct to the upstairs room?

Should I look at a direct-vent wall furnace (propane) for the upstairs room only and something different downstairs? Where to put a direct vent though??? There is only 1 outside wall, and when I ran all the electrical, conduits etc for the radio coaxes, I set it up to have the desk near that outside wall for access to the natural light of the window. May be enough room under the window for a small one...

And how many BTU's do I need for this upstairs room?

Note- that there is no insulation between the two floors aside from the attic space.

Thanks for your help guys!!

 

[Showkey]

With those "fuel prices" and the weather first thing I would do is double or triple the insulation especially in the highest ceiling areas. R-38 bare minimum but R-60 could be easliy justified.

(My son went to MTU......know the area well. We come back at least twice during the "summer." Camping and riding motorcycle and ATV)

 

[mygarageone]

Outside of more insulation , I would go with a hot dawg type unit for the garage and a small vented space htr for the upper room.
I would insulated the garage ceiling .
When are you planning on doing this ? I go up there several times a yr with my classic and for the car show . If your not in a hurry , I could help you equipment choice wise.
If your not going to be in the garage much , I certainly would do 2 separate units.

 

[histguy]

I agree that more insulation is needed, unfortunately the drywall has already been put in the upstairs room and OSB nailed to cover nearly everywhere else.

I do think I can get access above the room via the sides to get a hose up and blow some cellulose up there. Not ideal and I may not be able to get uniform coverage that way, but may be my only option aside from a major redo.

I want to get the heating solution for at least the room done in the next couple of weeks. The main garage area is not as critical this winter, it can be a summer project.

May concern is where to put the vented heater if I went that route. Only outside wall is in the front, so that seems to be the default, unless someone suggests a unique alternative.... But the propane will need to be in the back (opposite side) and the hot dawg would be in the back as well.

Thoughts?

 

[anthony666]

boiler in the fuel flavor of your choice, staple up in the upstairs room, hydronic unit heater downstairs

what do you have in the house ??

 

[histguy]

What do you mean by 'staple up in the upstairs room?

Can you send a quick link to an example/product website for this. I am not familiar.

Thanks.

(Propane Forced Air and a large wood pellet stove in the house)

 

[anthony666]

https://www.google.ca/search?q=stap...a=X&ei=vnbKVPL7B4qhyATbwoDAAQ&ved=0CAYQ_AUoAQ

so .. put a big pellet boiler in the yard, run underground lines into the house and shop .. yank the furnace and put an air handler with a hot water coil and an ecm motor .. and the previously stated staple up/unit heater in the shop

problem solved, bills in the mail

 

[JACDes]

Unit heater up stairs 30K BTU

Unit heater downstairs. 40K BTU

2:30 go home.

 

[mygarageone]

If it were me , I would go with a unvented unit up stairs and when your ready do the garage this summer.
I know you will hear all kind of reasons not to put in the unvented but I have used them for yrs with no ill effects and where your at it/s very dry in the winter and a little moisture would be helpful.
I heated a 700 sq foot cabin for 3 yrs and lived in it at the same time , didn't have as much as a head ache ever.
You can buy a thermostatic controlled unit that modulates from 10,000 - 30,000 btus
That would get you bye until you can do something different and then sell it at a yard sale up there and it will sell trust me.
I know your thinking what about my equipment , it won.t hurt it a bit , non of my stereo equipment suffered from the unit i used. There a whole lot more humidity up there in the summer than what that non vented unit will put out.

 

[theoldwizard1]

First, gorgeous garage you have there ! Near Houghton ?

so .. put a big pellet boiler in the yard, run underground lines into the house and shop .. yank the furnace and put an air handler with a hot water coil and an ecm motor .. and the previously stated staple up/unit heater in the shop

• Garn wood boiler. Load it once per day.

• Small pellet stove upstairs and a Protemp Sun Stream kerosene/diesel heater down stairs. These burn cleaner and with more heat than a "hot dog".

• I am familiar with the Keweenaw and I think you are being "generous" saying "Below zero temps are not uncommon, but also do not last for long stretches. Common temp around 15-20 from Dec-March." In most of MI, a good "low temp" mini-split heat pump would work well for both upstairs and downstairs. These are much more efficient than straight resistance heat. Also usually much cheaper than propane.
  
  Unless you plan on using the lower level a lot, just use the mini=split upstairs and the Protemp Sun Stream downstairs.

This is from a Mitsubishi Hyper Heat brochure. I would be concerned about the number of hours of below 0F outside temps that you get.

View media item 43975

Bonus, you get free A/C for the couple of days a year when the temp hits 80 !

 

[Showkey]

Have you seen the price of kerosene ?????

I would stick with propane or even .24 kW electricity.

 

[danski0224]

Why make it complicated?

You don't have natural gas.

You don't want to pay for electricity.

You don't want to modify the existing structure to improve insulation.

That pretty much leaves some type of propane forced air or radiant* system. Even with a heat pump, some type of backup heat may be needed- whether it is electric strip or fossil fuel.

Just keep in mind that redoing the structure to improve insulation and weather sealing will be cheaper in the long run vs a high dollar/high tech heating solution.

With only R-19 in the ceiling/roof, you are fighting a losing battle with expensive heat like propane or electric resistance. The attic/roof should be a minimum of R44. The attic/roof is your greatest source of heat loss. There should be an airspace between the insulation and the roof deck, and the insulation in a roof/ceiling combination should be touching rigid building materials on all 6 sides (airstopping). Cramming R19 batts between the trusses or stick framing with the batting touching the roof deck and having soffit and ridge vents virtually negates any R value.

I bet that your knee walls are not insulated properly, either. Are those doors insulated and weatherstripped exterior doors? They should be- that "unconditioned space" is "outside". Sure, you have "not heated" on the drawing, but if the thermal boundary is not defined properly, then the space is heated, whether you want it or not.

You should either pay for a load calculation or do it yourself. Search the Web for info on that.

It is assumed that a direct vent wall unit will work, but you do not know for sure until the load is figured.

Radiant in this case refers to infrared, like tubes or ceramic... not hydronic.

 

[theoldwizard1]

Even with a heat pump, some type of backup heat may be needed- whether it is electric strip or fossil fuel.

TRUE ! Which is why I recommend a Protemp Sun Stream kerosene/diesel heater for down stairs

 

[finn]

I'm down the street from you, on the lake in East Grosse Pte. Shores.

Call the heating guy in Bootjack for an equipment recommendation. He has the best installed prices locally, in my experience, and he returns your phone calls, which is rare for a tradesman.

PM me and I'll give you his name, along with another local guy.

Frankly, I'd skip right to a high efficiency forced air propane residential type furnace in your situation. Some of the lesser brands are priced reasonably, and with the volatility of propane pricing, I'd opt for something with a ~95% efficiency, as opposed to 80% or worse with hanging unit heaters.

You'll need minimal ducting, so the biggest installation cost will be running the gas line from the regulator to the unit. Exhaust is PVC, so you avoid the cost of catIII (or whatever it is) exhaust piping, and you don't have to penetrate your roof.

I installed a hanging unit heater in my home garage and a HE propane forced air furnace in a house I'm rehabbing, both this fall. The extra cost for the furnace was worth it.

Pellet stoves are also interesting, but at ~$247/ ton (last I checked) and with the added maintenance, etc., they are probably a no go for full time heat.

 

[histguy]

Thank you everyone for the thoughts and suggestions thus far:

First to respond to some of the questions by danski0224:

- Knee walls are properly insulated and vented. The existing insulation is properly installed, despite the low R-value. There is significant air space between the ceiling and the roof. Doors are insulated and weatherstripped.

Previous owner used the space as an occasional workshop for a side business. Just ran space heaters for the occasional time he was up there. I suspect that went into his decision to insulate-on-the-cheap.

Thanks for the suggestion to do a load calculation. According to www.loadcalc.net I need 10,000 BTU's for the upstairs room...

I did the knee wall, cellulose work in preparation for this upgrade.

- Finn- Nice to stumble across a neighbor on here! I will PM you for the name of the guy in bootjack for his thoughts as well. A pellet stove is not ideal for the garage. They take quite a bit of time to warm a space and require daily maintenance. Fuel prices are better than some options but not given the inconvenience of pellet storage (already buying & storing 8 tons a year to burn in the house) and the daily maintenance.

- theoldwizard1- Thanks for the recommendations. It really does not get that cold that often up here on the Keweenaw. I have a professional weather station here and keep detailed records on such things. Only 3 days in January below 0, and average temp for the month was 19.2. So cold yes, but not Alaska cold (spent many of years up there...)

Not sure the heat pump is a good solution for the investment and the way I use the space. Key is to have a simple low maintenance solution to keep the upstairs room at 45 or so, with a reasonable cost way to bring the temp to 65 for a couple hours here and there a few times a week.

The downstairs really can be unheated most of the time. Most of the time it is around 27 in there, unheated (14 outside right now, 29 in garage). Would like a simple solution to get it to 45-50 when I want to work on the car/bike/sled, etc.

Looked at the the Sun Stream idea. That might work for the downstairs. Am I correct that they run more efficiently than the hanging heaters?

Leaning towards a direct vent for upstairs... You can set them and forget them for my 45 degree needs. And heat the space rather quickly for the other times. While in Alaska, I heated my entire 1600 sq.ft A-frame house with only a single 38,000 BTU direct vent wall furnace. Surely I can heat a less than perfectly insulated 250 sq. ft room rather easily with either the 14,000 BTU on from Williams or this 11,000 one from Rinnai (I had their 38K one in AK, worked amazing for many years)

http://williamscomfortprod.com/product/direct-vent-furnaces/

http://www.amazon.com/dp/B004H7T3N2/?tag=atomicindus08-20

 

[danski0224]

- Knee walls are properly insulated and vented. The existing insulation is properly installed, despite the low R-value. There is significant air space between the ceiling and the roof. Doors are insulated and weatherstripped.

Just curious as to what is visible on the unfinished side of the kneewalls.

Fiberglass/wall insulation or something else?

 

[histguy]

I put "solar-guard" ontop of the fiberglass batts that are between the kneewall and the heated space. I understand this to be correct?

 

[danski0224]

All that is needed is an air barrier on top of the fiberglass... plywood with taped/sealed seams, firetaped drywall, extruded foam (if local codes allow exposed foam board)...

Whether or not the foil insulation is "better", there are plenty of dubious claims made by manufacturers of similar products over the years.

 

[ksj9393]

Histguy - There's some excellent advice in the posts so far. I think Danski summed up the parameter boundaries well. I would second the advice of performing a rigorous heat load calc - 10K for the loft with your current thermal envelope sounds about right.

I have a similar situation here in MN, and while technically its my "back-up" heat source, I am now sold on mini-split heat pumps. With your temps in the U.P., they would perform fine. I have a 9K BTU head in my loft, and 12K BTU head in my shop area, and they are superb. Though electric, they are efficient. I spent about $4,000 for the install, so while not exactly cheap, the energy efficiency should pay of in a situation such as yours in, I would guess, a decade or two.

I would also do everything you can to air seal your garage as well as possible... the air-barrier that Danski speaks of. And considering increasing the R-value if possible. "Solar-guard" and the like is a wast of time effort and most importantly, money, in my opinion. Air seal, insulate, and select an energy efficient heat source.

P.S. Do NOT go with unvented propane heater unless you have an incredibly leaky garage and choose to ignore the advice given above! Speaking from experience...

 

[histguy]

ksj9393, thanks for the 2nd on danski. I got the 'solar-guard' from a guy cheap, 2nd hand (left overs from a project), so spent quite little on it.

What I will go back and do though is to seal it up well as you suggest. Caulking, spray foam etc.

I like the idea of the mini-split, unsure the investment for the garage makes sense. Will however looking into it for the house for sure! She is 130 years old and is leaky like crazy. That is the summer project!

 

[theoldwizard1]

Not sure the heat pump is a good solution for the investment and the way I use the space. Key is to have a simple low maintenance solution to keep the upstairs room at 45 or so, with a reasonable cost way to bring the temp to 65 for a couple hours here and there a few times a week.

A modern, high efficiency, low temp, mini split heat pump is PERFECT for that application. The only issue is if the thermostat will will go down to 45° ! People have a hard time understanding that a heat pump can move "heat" from outside (yes, even at 5°) to inside. and doing it more efficiently than electric resistance heat ! Propane prices vary from place to place. I can't prove it, but I think a mini split would eb cheaper to operate than a propane furnace.

Leaning towards a direct vent for upstairs... You can set them and forget them for my 45 degree needs. And heat the space rather quickly for the other times.

Those do work well and are a lot less expensive to install compared to a mini split heat pump. I have no idea how to compare the cost of propane for one of those versus electricity for a mini-split.

Looked at the the Sun Stream idea. That might work for the downstairs. Am I correct that they run more efficiently than the hanging heaters?

Again, this is an apples to oranges comparison. A typical garage hanging furnace would be electric or propane. The Sun Stream runs on kerosene or diesel.

My gut says the Sun Stream is cheaper to operate than electric or propane, but I can't prove it. I like it because it IS portable and can be used inside of a home (very low CO and CO2).

 

[danski0224]

I wouldn't say that the reflective "insulation" products are a waste of money- there is validity to the reflective properties. The insulating or R values are another matter entirely.

I put some reflective stuff in a van with a small air gap on the side panels and roof, and the solar gain was decreased dramatically.

I have a traditional split system heat pump in my home with fossil fuel backup. Right now, it is cheaper to run natural gas heat pretty much 100% of the time. That wasn't the case when it was installed, and who knows what the future holds.

It is very difficult to honestly project "payback" or ROI on efficiency improvements because energy costs always change. The other reason is that there are many other dynamics that impact how a structure heats or cools.

The lowest initial cost heating system would be 2 direct vent propane fired wall heaters. This leaves you 100% exposed to the volatility of propane pricing and availability.

Next best would be the fancy heat pump mini-split with the same propane fired heaters as backup. Integrating the controls here may be a challenge if the OEM mini-split thermostats do not interface with an emergency/backup heating system. If there is a substantial cost difference between the Mitsubishi Hyper Heat/Y series/standard mini-split, then that cost difference is weighed between the cost of the backup heating system and fuel costs/options. Heat pumps can deliver $4 worth of heat for $1 worth of electricity through the magic of refrigeration.

I can set the balance point on my thermostat, and it automatically switches between heat pump mode and backup/emergency heat based on outdoor temperature. Economic balance point is calculated based upon electrical costs and natural gas costs and equipment heat output at 47* (manufacturer spec), and this is not necessarily the same as the straight balance point. My heat pump will heat my home when it is 20* outside, but the economic balance point (last I checked) is with a 55* outdoor temperature. As the outdoor temperature drops to the balance point, the heat pump will run 100% of the time, excluding defrost cycles. Vent temperature is cooler than gas or oil, and that is an issue with some people- besides the increased fan-on time.

If all you need is 10,000 btu to maintain 70*F, that can be accomplished with about 4kW of resistance strip heat... about $500.00 in 240v baseboards.

One caution on the fancy mini-splits (and tankless water heaters) is that they are extremely complicated pieces of equipment with extensive computer controls. Economical or speedy repair is probably not likely. Your average DIY or HVAC pro will not be able to fix it, and tech support will resort to board swapping.

 

[Jackfre]

Rinnai EX22 or 38. 2 1/2" hole in wall for vent. Sealed combustion, 7 stage modulating gas valve and blower, 7 day programmable stat built in, cool to the touch, simple install, very reliable. Through its modulation the 22 draws between 33-56 watts. Not cheap, but you get your monies worth.

 

[danski0224]

My gut says the Sun Stream is cheaper to operate than electric or propane, but I can't prove it. I like it because it IS portable and can be used inside of a home (very low CO and CO2).

For propane/diesel/kerosene, you need quantity of btu's per gallon and cost per gallon.

That Sun Stream claims 70k btu for 7 hours on 4 gallons, so it is using 1.75 gallons per hour.

Electric is pretty much ~3.4 btu/watt or ~3,400 btu per kW. So you would need electrical cost per kW/Hr. 3.4 kW x $0.24 per kW/Hr = $0.816 per hour to run a 3400 watt heater.

 

[Showkey]

+ 5 ^^^^^^^^^^^^^^^^^^^

My gut and experience was think kero and electric was not a good choice for the $$$$$ and danski proves that point. I to have been down the unvented heaters with kero, propane and NG never again in a reasonable tight structure. Maybe in a leaky garage in a pinch but not as permanet solution.

Plus kero by itself stinks no matter the heater........and burning will create more odor than the unburned liquid with can be detected in a small room like we talking about.

Then the cost of kero and inconvience of fueling the device makes it a non starter.

That Rinnai unit has real merit.

 

[danski0224]

I installed one of those Rinnai units, and it was nice.

 

[brewchief]

I would go with either 1 direct vent heater and 1 hanging unit heater or 2 direct vent heaters.

The mini split heat pump would be on the radar IF I needed A/C, yes they are efficient but the OP still has a high electric rate and may have to spend a bunch of the winter shoveling the area around the unit unless it's mounted 10ft up on the sidewall.

We priced one of the hyper heat Mitsubishis for a job recently and it was big bucks compared even to a standard heat pump mini.

 

[Showkey]

I installed one of those Rinnai units, and it was nice.

After see this posting.....I was looking for a supplemental heat unit for a basement ...........the Rinnai is now first on my list. Went online to read the install manual. Looks like they allow 60-80" vent piping. My shirt area is two feet off the ground so venting through the skirt look easy and possible. Especially with the small diameter pipe used on these units.

Many other units use a 3-4" or even 6" pipe.

It's colder in Wausau than where the OP is ( he got Lake Superior to warm him up) ........so a split system is not on my list. We pay .12 kW all in with all fees.

 

[danski0224]

A customer found the Rinnai unit online, and a local distributor would not order it for me. The customer then ordered it from Amazon. It is a nicely made unit, much better construction than a Williams wall heater, but the price refects that. Installation was pretty straightforward.

 

[theoldwizard1]

i have a traditional split system heat pump in my home with fossil fuel backup. right now, it is cheaper to run natural gas heat pretty much 100% of the time. that wasn't the case when it was installed, and who knows what the future holds.

It is very difficult to honestly project "payback" or roi on efficiency improvements because energy costs always change. The other reason is that there are many other dynamics that impact how a structure heats or cools.

The lowest initial cost heating system would be 2 direct vent propane fired wall heaters. this leaves you 100% exposed to the volatility of propane pricing and availability.

EXCELLENT SUMMARY !!

 

[theoldwizard1]

... he's got Lake Superior to warm him up ...

What an oxymoron !

 

[theoldwizard1]

A customer found the Rinnai unit online, and a local distributor would not order it for me. The customer then ordered it from Amazon. It is a nicely made unit, much better construction than a Williams wall heater, but the price refects that.

Yeah, OUCH !!!

 

[danski0224]

I would go with either 1 direct vent heater and 1 hanging unit heater or 2 direct vent heaters.

The mini split heat pump would be on the radar IF I needed A/C, yes they are efficient but the OP still has a high electric rate and may have to spend a bunch of the winter shoveling the area around the unit unless it's mounted 10ft up on the sidewall.

We priced one of the hyper heat Mitsubishis for a job recently and it was big bucks compared even to a standard heat pump mini.

I wouldn't automatically dismiss the heat pump option without doing a balance point calculation... unless the customer specifies cheapest initial way to do the job.

Even if a standard mini-split can heat down to 10*F, that is a substantial portion of the heating season not on propane. Controls interfacing would/could be the stumbling block.

I would probably use the highest cost of propane over the last 24 months or so to base the calculation on- especially if the OP doesn't get the tank topped off in July... Electric costs are more stable, at least in my area.

 

[theoldwizard1]

IThe mini split heat pump would be on the radar IF I needed A/C, yes they are efficient but the OP still has a high electric rate ...

No question if A/C is a requirement. I depends on the cost of propane versus electricity in his area and which is more likely to change (go up or down) in the next couple of years. Hard to predict.

With the price of oil and natural gas so low, I would expect propane would be low at the moment.

and may have to spend a bunch of the winter shoveling the area around the unit unless it's mounted 10ft up on the sidewall.

Yeah, 10' should be high enough ! Unless it is a side of the building that gets wind blown drifts. Then it had better be 15' !

We priced one of the hyper heat Mitsubishis for a job recently and it was big bucks compared even to a standard heat pump mini.

Quality is not cheap.

 

[danski0224]

Yeah, OUCH !!!

Small unit size, virtually silent, remote control, small external termination, almost zero clearance to combustibles at the vent termination, no condensate drain needed...

Those are all huge plusses for that unit.

 

[danski0224]

With the price of oil and natural gas so low, I would expect propane would be low at the moment.

Quality is not cheap.

Anyone with half a brain should know that the current low oil price is an anomaly driven by politics. The potential for major geopolitical upheaval is real.

The prior high price was driven by Wall Street speculators, not supply and demand.

There *is* a glut of natural gas, with who knows how many thousands of cubic feet flared off daily (instead of captured) at the fracking sites. It is reasonable to assume that this will change at some point.

I would base any long term energy costs and energy use decisions on the prior high price vs the current fake low price.

It will be cheaper long term to redo the interior of the structure and insulate it properly- especially with such a small space. This means smaller heating equipment and btu (cost) requirements.

Quality is never cheap.

 

[Jackfre]

After see this posting.....I was looking for a supplemental heat unit for a basement ...........the Rinnai is now first on my list. Went online to read the install manual. Looks like they allow 60-80" vent piping. My shirt area is two feet off the ground so venting through the skirt look easy and possible. Especially with the small diameter pipe used on these units.

Many other units use a 3-4" or even 6" pipe.

It's colder in Wausau than where the OP is ( he got Lake Superior to warm him up) ........so a split system is not on my list. We pay .12 kW all in with all fees.

The vent extension guidelines vary by model. For instance, the smallest unit, the 08 cannot use the extensions at all due to only a 3-8000 input, the 11 can use them, but again, limited. The 17, 22 & 38 units can handle longer runs. Be sure to check the manual for the particular model prior to deciding if it will handle it. I can answer any questions you have on these.

 

[histguy]

Thanks to everyone for their fantastic thoughts and advice. Great stuff here guys.

So here is a fairly long post with the results of my research and analysis. I would appreciate getting peoples thoughts on these numbers and my overall plan.

1st- I am not going to worry about heating the downstairs right now. That is not a major concern. I am going to go with the sunstream like forced air diesel/kerosene as a temporary solution. Only $180 for a 75K BTU one. Will be fine for now and we revist perhaps in the future. Just doesn't make sense to heat that space all winter with something more permanent.

Now for heating the room above (my primary concern)

I played with a number of heat load calculators, they are all a bit different. Settled on the results from the one provided by Rinnai, because it allowed me to input the most detail about the buildings, climate, envelopes, insulation, openings etc. Check it out here:

http://heatload.rinnai.us/#

I used all the info and inputted both a 45°F heating setpoint (what I call my maintence temp- I don't want it below this temp at any time) and a 65°F setpoint for when I am in there (with the lights on, radios, computers etc, I would not set the temp on the furnace above this)

I said that the room was 'semi-loose' as far as tightness goes. I see that I can improve this quite a bit, but figured this was way to keep the math very conservative!

Here are the results (questions follow below)

45°F as currently insulated

The heat loss by envelope

The resulting BTU needs:

65°F as currently insulated

What is clearly obvious to me (and to my surprize was not pickup in the conversation to date), is the need to insulate the floor in this room!!! So I re-ran the calculations with using R-13 batts between the two floors (best R-rating to $$ I can buy locally)

45°F after insulating the floor

65°F after insulating the floor

What a significant difference!!! About 40% less BTU's needed.

Costs

I then wanted to see what the costs are to heat using propane and one of these Rinnai units (all models at 82% efficient)

Given that the room stays a rather 25°F constant right now when the outside temp is between 0°-15°F outside, I factored that to get to 45°F I need 20° increase (and thus 40° when using the room)

Output BTU needed ÷ 0.82 (efficiency) = input to furnace BTU's.

Input to furnace BTU's ÷ 91,500 (BTU's per gallon of propane) = # of gallon's of propane used per hour.

# of gallon's of propane used per hour x price of propane per gallon= cost per hour

My current cost for propane is $1.80/gallon. I alway buy a contract in mid-summer. Last year was $2.05

So I used $2/gallon for this analysis (yes I know it can go up and down!)

So for current insulation @ 45°F= $.25/hour or $182/month

If I insulate the floor.... @ 45°F= $.15/hour or $110/month

So a no brainer to insulate the floor. It will pay itself back in less than one winter.

Questions

1. Does the BTU needs from Rinnai's site make sense?
2. Given that I need 5800 BTU's to keep the room at 45° and 8,100 for 65°. Should I go with a EX11 http://www.rinnai.us/direct-vent-wall-furnace/product/ex11c_rhfe-265fta#tabs-2 over an EX-17? http://www.rinnai.us/direct-vent-wall-furnace/product/ex17c_rhfe-434fta#tabs-2. Though I like the idea of having extra BTU with the larger model incase my analysis is wrong.

I am thinking so because the EX-17 has a minimum input BTU of 8,200 and the EX11 has a minimum of 5,500. Would I not be wasting gas with the larger model when I am at maintenance temperature?

Thanks guys. Hope this helps others also.

 

[danski0224]

When you insulate the floor, the insulation must be touching building materials on all 6 sides to provide the rated R value.

If the plan is to stick R13 batts in the joist spaces with an airspace either from the floor above down or drywall ceiling up, you will not get the rated R value.

Oh, and AFUE is kind of a made up number, it does not, in any way, reflect the actual true combustion efficiency of the appliance.

 

[histguy]

When you insulate the floor, the insulation must be touching building materials on all 6 sides to provide the rated R value.

If the plan is to stick R13 batts in the joist spaces with an airspace either from the floor above down or drywall ceiling up, you will not get the rated R value.

Thanks for this advice. Batts will touch on 5 sides, will need to think about best way to cover (which admittedly will be a pain with all the **** that is hanging from the ceiling right now) May go with a higher R-valued batt for now and when able return to cover with OSB (What the rest of the garage is covered with except the room above) when time permits (time is short...)

Thanks.