# Do you know how many BTU's per year you need for heating?



## ABMax24 (Nov 23, 2019)

Reading some of the threads on this forum I am astounded by the amount of energy some members are using to heat their homes. Some are using close to 10 cords of wood plus hundreds of gallons of heating oil, or some other alternative fuel source. So I figure I'll calculate my heating load and post it in the hope others will do the same and we can have some data to compare.

I figure the following would be helpful for comparisons:
House and Climate; house location,heating degree days, heated size in sqft
Insulation; attic, walls, basement, windows
Fuel consumption of various types; gas, propane, oil, wood, coal, electric, etc.
Total energy per year in BTU

So since our wood stove was just installed this fall I don't have enough data so will include gas heat from previous years.

On top of the below we also annually consume 2,600 kwh of electricity, but this solely runs the lights, fridge, freezer and electronics.

Heating 2100sqft house with 2 floors + basement in Northwestern Alberta. 5,851 Heating Degree Days Celsius. (10,531 HDD Fahrenheit)
R-50 Insulation in attic, R-22 insulation in exterior walls, and R-22 insulated Basement walls, non-insulated basement slab.
Natural Gas used for: space heating, water heating, gas range, gas dryer, garage heater, BBQ (Gas and Electric are only options, electric is 5x cost of gas per BTU)
Annual Usage: 82,000 cubic feet of natural gas, or 85.4 million BTU.


----------



## Seasoned Oak (Nov 23, 2019)

At one time i used up to 4+ tanks of oil a year or about 140 -160 million BTUs to heat just under  3000 Sqft of poorly insulated house to 72 deg . Over the yrs i have reduced that to between 70 to 90 M BTUs .(Depending on winter severity) thru a combination of adding insulation and adding a Sun room on the south side of the house. Im now heating to 76 Deg. Still more room for improvement i know.


----------



## Brian26 (Nov 23, 2019)

Here are my numbers. They are extremely accurate based on fuel consumption of my oil furnace. I used an ultrasonic fuel gauge with .1 gallon resolution to get the numbers.

32 degrees. Heat loss of around 10-12k btu/Hr
10 degrees. Heat loss  of around  20-25 btu/hr

1958 1600 sqft house about a mile from the shoreline in the New Haven CT area. 8 inches of blown loose cellulose in the attic. Original fiberglass insulation with r3 foamboard under the vinyl siding. All new andersen 70 series windows. Extensive leak sealing in basement and attic with spray foam. The foundation is currently getting r10 foam board put up.

My insanely oversized 90k btu oil furnace is used mainly during extreme cold to run the whole house humidifier. I use 2 12k mini splits probably 80 percent of the time for my heating needs. Mini split cutoff temp and switch to oil is 15 degrees. Here on the CT shoreline those temps are rare.


----------



## ABMax24 (Nov 23, 2019)

Brian26 said:


> Here are my numbers. They are extremely accurate based on fuel consumption of my oil furnace. I used an ultrasonic fuel gauge with .1 gallon resolution to get the numbers.
> 
> 32 degrees. Heat loss of around 10-12k btu/Hr
> 10 degrees. Heat loss  of around  20-25 btu/hr
> ...



I guess I never thought to do it in BTU/hr. I did check and over 2 -40 days last year I used 1600 cubic feet of gas, for a heat loss of about 35k BTU/hr. That's pretty significant heat loss considering my furnace is only 80k BTU, makes sense why it runs so much in those temps.


----------



## DBoon (Nov 24, 2019)

I have three data points - a condo an hour north of NY city, a small 1920s bungalow in Central NY and a partially remodeled larger 1920s bungalow in Central NY.  

Condo
Climate: Zone 5, ~6000 degree days per year, ~1200 square feet
Insulation: first floor of two-floor flat, so no attic, walls on sides, so just two walls exposed with R-13, plus walkout basement with R-20 walls (remodeled), windows new and R-5.
Fuel: for heating, formerly natural gas (primarily), now Mitsubishi mini-split heat pump
Heat Loss: About 10 kBTU/hour at 0 degree F outdoor
Total energy per year in BTU: About 25-30 MBTU/year (gas)

Small Bungalow
Climate: Zone 4, ~7500 degree days per year, ~1250 square feet
Insulation: R-13 walls (blown-in fiberglass), R-50 attic, R-19 floor over basement, R-2 windows (single-pane with storms).
Fuel: for heating, oil (boiler with radiators) and wood (wood stove) and now Fujitsu mini-split heat pump
Heat Loss: About 22 kBTU/hour at 0 degree F outdoor
Total energy per year in BTU: About 65 MBTU/year (usually about 300 gallons of oil, balance wood, but hoping that mini-split will reduce oil usage to <100 gallons per year)

Large Bungalow
Climate: Zone 4, ~7500 degree days per year, ~1750 square feet
Insulation: R-20 walls, R-50 attic, R-19 floor over basement, mix of R-2 (single-pane with storms) and R-5 windows.
Fuel: for heating, geothermal heat pump (electric) with radiant floor heating
Heat Loss: About 18 kBTU/hour at 0 degree F outdoor
Total energy per year in BTU: About  52 MBTU/year (electric)


----------



## DickRussell (Nov 24, 2019)

My annual home heat loss calculation is based on limited data. Location is lakes region NH, annual heating degree days ~7500 F. House is about 4,000 sq.ft. total conditioned space on two levels, double exterior wall frame with 12" insulation cavity (~R40), R60 attic, R20 on foundation walls and under slab, triple pane windows, very low air leakage, ventilation 24/7 via HRV. Heat is by two-ton ground source heat pump.  Best calculation is backed out of hour meter over three-day cold snap with outside temps swinging a few degrees to either side of zero, giving about 19,000 BTU/hr with inside at 70, outside at zero. Calculating out for the year on that basis gives 52 million BTU/yr.


----------



## DBoon (Nov 24, 2019)

Pretty impressive performance, DickRussell. I have a 3 ton GSHP with a 180 gallon storage tank and I can say that it has yet to run near 50% duty cycle. Someday, I may upgrade to a very large storage tank (home built) and just run the GSHP during solar PV production periods and then draw from the tank as required overnight.


----------



## ABMax24 (Nov 24, 2019)

I like adding the heating degree days, I have updated the first post. Turns out I'm over 10,000F HDD.


----------



## byQ (Nov 24, 2019)

I'm building a small house, zone 5, Idaho, but I don't know the heating/cooling requirements of it yet. I'm doing some passive solar concepts - large south facing windows, windows inset, internal thermal shutters, and  black thermal mass to absorb sun.  I found some big black porcelain tiles at Lowe's.

The color black can absorb the sun's energy the best - it is surprising, it is like twice as effective as some lighter natural colors (so twice the heat energy). How much heat input into the house directly from the sun? I'm not sure.
My second form of heating will be from a masonry heater. That's it. If I leave on vacation I will need to plug in a heater.

A 3" or 4" dark masonry inner wall is supposed to work best.  The wall absorbs the sun during the day and after the sun goes down (shutters closed) the wall radiates the heat into the living space until the cycle begins anew. Moreover, water is superior to masonry in collecting heat so I'm going to try to incorporate some metal black 55-gallon water filled drums into the inner wall (they'll be hidden). Worst case scenario - this house completely heated by the sun. This would mean no burning in the masonry heater unless cloudy or very cold. Here is a picture of the outside.


----------



## Seasoned Oak (Nov 24, 2019)

byQ said:


> and  black thermal mass to absorb sun.  I found some big black porcelain tiles at Lowe's.
> 
> The color black can absorb the sun's energy the best - it is surprising, it is like twice as effective as some lighter natural colors (so twice the heat energy). How much heat input into the house directly from the sun? I'm not sure.


I used the very dark grey as opposed to flat black on the floor ,was considering going halfway up the wall since the sun shines halfway up the wall Dec 21,but ultimately just did the floor. They still get up to 140 degrees F while the sun is shining.  Cant walk on them in bare feet.  If id done the wall too it probably would get too hot in that room.
Goes up to 120 on a sunny winter day.


----------



## thrifty (Nov 29, 2019)

When I bought my 1954 1228 sq. ft. rambler in  2000. The heating degree days total for the first year was 8074. I used only the forced air gas furnace for space heating and a gas water heater and gas dryer. 91,700,000 BTUs $877 Nat gas for the year. I covered all the windows with plastic film, wrapped the water heater with fiberglass. Later I more than doubled my attic insulation with recycled unfaced fiberglass batts. Since  2004 I have used a wood burning insert burning around 2  (4x4x8) cords or a little more per year. In 2018 ( heating degree days 8054) I used 9,000,000 BTUs $167 Nat. gas. The house is cooler but the cost savings is significant as my insert and firewood are free. Electric use 2,227kwh for 2018. Water use 16 gallons per day. Gasoline 3 gallons per month.


----------



## JRHAWK9 (Nov 30, 2019)

This maybe a dumb question, but how are you guys calculating your heat loss based on fuel consumption and HDD's?

I keep track of lbs wood burned, minutes my 75KBTU LP furnace runs and HDD's.

Last winter I burned 17,100lbs of wood and the LP furnace ran 25 hours (mostly when we were not home).

So, assuming 6,500BTU's per LB of wood and taking into account efficiency of both my wood furnace and LP furnace, I come up with a total use of 95,952,000 BTU's, of which only 1,524,000 was LP.  Total HDD's were 7,990. 

Before we heated with wood we averaged about 1,300gal of LP a year (averaged over 4 years).  Based on what we use now, our LP water heater and clothes drier account for a little less than 100 gallons a year between the two of them.  So roughly 1,200 gallons of LP was going to heat the house, keeping it only at 68°.


----------



## DBoon (Nov 30, 2019)

JRHAWK9 said:


> This maybe a dumb question, but how are you guys calculating your heat loss


Not a dumb question at all. I've done it two ways:

 I've built an Excel spreadsheet that I use to do a room-by-room heat loss calculation using wall, ceiling, floor, window, door, etc. square footage and U-value (inverse of R-value). Then, I can input an indoor and outdoor temperature and calculate heat loss. It's been pretty accurate. At my small village house, I double-checked it against degree days for the season and oil usage for the same season, and it my renovation I've compared my expected radiant heat temperature settings to actual to maintain a given indoor temperature. 
In my condo, I had a small gas heater that just put out 8,000 BTUs (net) on low constantly. I knew the outside temperature where that would just run constantly and keep the house at a stable temperature, so I could just calculate the 0 degree heat requirement from there.


----------



## Seasoned Oak (Nov 30, 2019)

I use my previous oil consumption to gauge my progress in improving heating efficiency. Thats really all i need to know.  From here on out all improvements will come at a greater cost vs payback.


----------



## JRHAWK9 (Nov 30, 2019)

DBoon said:


> Not a dumb question at all. I've done it two ways:
> 
> I've built an Excel spreadsheet that I use to do a room-by-room heat loss calculation using wall, ceiling, floor, window, door, etc. square footage and U-value (inverse of R-value). Then, I can input an indoor and outdoor temperature and calculate heat loss. It's been pretty accurate. At my small village house, I double-checked it against degree days for the season and oil usage for the same season, and it my renovation I've compared my expected radiant heat temperature settings to actual to maintain a given indoor temperature.
> In my condo, I had a small gas heater that just put out 8,000 BTUs (net) on low constantly. I knew the outside temperature where that would just run constantly and keep the house at a stable temperature, so I could just calculate the 0 degree heat requirement from there.




I used -THIS- calculator and this is the result:





Our house is definitely not careful new construction.  It's a log cabin style with loft.  We lose a lot of heat at the peak.


----------

