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Why Is House Cold With Heating On

house cold

This is my own boiler. If the outdoor temperature drops below 5 F, the house loses more heat each hour than the boiler is able to produce in an hour. The colder it gets outdoors the colder it starts to get indoors. Copyright 2018 Tim Carter

You wake up on a frigid morning or come home from work and your house is cold, yet the heater or furnace is on.

You might mumble out loud as you shiver, "Why is house cold with heating on?"

Why Is House Cold? Furnaces Can Only Do So Much

Here's why your house is cold when your heating is running non stop:

  • Furnaces, boilers and electric heaters can only generate X amount of heat per hour
  • Think how shoes, clothes and hats come in different sizes - so to heaters
  • Your builder / HVAC man installed a heater sized for an average low temperature in your city/town

Related Links

Heat Loss Explained - Sizing Heaters and Furnaces

Electric Floor Heat - Very Cozy But Can Be Expensive

Candle in a Warehouse Example

I can explain why you're shivering with this example. Imagine if you had a standard candle and you were in the middle of a large warehouse.

The first thing to remember is there's no way the candle can produce enough heat in one hour to heat up the warehouse to a comfortable temperature.

But put that candle inside a small picnic cooler container and the temperature will get nice and warm in a short amount of time.

Free and Fast Bids

CLICK HERE to get FRE & FAST BIDS from local heating companies that can install a LARGER heater.

Heat Loss Calculations - This Is The Secret

Another key point is heat loss. Your home has a distinct heat loss each hour. Imagine if your house was 70 F inside and it was 0 F outside.

If your power went out and your heater stopped working, the temperature inside starts to drop. Each hour it gets colder and colder because of this heat loss.

Your home may lose heat faster than a neighbor's home because your home has:

  • poor insulation
  • many air leaks
  • ill-fitting weatherstripping around doors and windows
  • lots of windows and doors

It must be remembered that each house has it's own heat loss per hour. A point often overlooked is that your heater, furnace or boiler also can only produce a given amount of heat per hour like the candle above!

As soon as the heat loss per hour is GREATER THAN the heat per hour the heater can produce, your house starts to get uncomfortable. As the outdoor temperature drops lower and lower, it gets colder in your home.

Your Heater Is Sized for AVERAGE Low Temperature

Your heater or furnace is sized according to an average LOW temperature in your city or town.

In other words, it would be wasteful to install a heater in your home that would produce enough heat each hour to heat the giant warehouse we discussed. That would be overkill and waste lots of your money.

Most of the time your heater keeps you comfortable because the outdoor temperature is at or ABOVE the average low outdoor temperature.

Sooner or later bitter cold weather happens and your furnace or heater just can't keep up.

How to Stay Warm in a Cold House!

cold house knit hat

This is how I'm dressed in my cold man cave! Note knit hat, fleece vest, fleece light jacket. You can't see my long underwear and wool socks! Copyright 2018 Tim Carter

It's easy to stay warm when your house is cold. Just do the following:

  • wear long underwear inside
  • put on a knit hat
  • wear wool socks
  • put on layers inside - even a fleece jacket
  • add a SAFE amount of humidity to the air inside your home

CLICK HERE to read all of my past columns dealing with humidifiers, how to set them, alternative ways to add humidity, etc.

These things retain more of your body heat and believe me you'll stay warm!

CLICK HERE to get FRE & FAST BIDS from local heating companies that can install a LARGER heater.



23 Responses to Why Is House Cold With Heating On

  1. Tim, Great article! I own a wood frame, balloon construction 2 1/2 story dutch colonial house built in 1922. I bought it in 1982, first call when I took possession was to a high school friend in the insulation business. He blew in cellulose to "help" reduce heat loose. I have a front porch with ten double hung windows, basically three glass walls, and quickly realized that with the reduced heat lose because of he insulation the boiler (steam heat) ran less often which made for larger temperature swings in the porch. The following year the steam radiators came out and hot water baseboard installed with it's own thermostat, problem "basically" corrected. Not often, but, on occasion, the baseboard has trouble keeping up with heat lose, as you mentioned, time for more clothes. The main and porch thermostats are programmable, and, realizing the boiler can only do so much at a time, the main house is programmed to come up to temperature before the porch. An idea I have had, but not implemented, was to install a relay to interrupt the porch heating signal when the main house thermostat is calling for heat.
    Thank you for your news letters, tips, and information!

  2. I just got a Nest thermostat, and it tells me how long the furnace runs. On that day that it went to 20 below at night, it ran for 7-1/4 hours. We have a bit of insulation (R-30 ceiling) and I've tightened up a bit (actually I'm considering an air/air heat exchanger) and some solar heating. We have the smallest high efficiency furnace we could find (80K BTU). Our total National Grid bill averages $110.

    Maybe you have a window open, or maybe you need some insulation.

  3. Thanks for the wisdom so often needed to help your readers not jump to the wrong conclusions. However, must point out that, although you sagely note that a call to a furnace repair company is probably not needed, the ads for a "bigger furnace" may push some of those who don't need a bigger furnace to wonder if they do. I try to support your site with Amazon buys because I appreciate (and need) your advice. I wish amazon would not take advantage of your reputation.

  4. When we specified the heating system for our house, replacing an old 300,000 BTU boiler, we used a 100 F differential. -30 outside and 70 F inside. I ran the numbers and the HVAC company ran them and we both came in at about 90,000 BTU. If I remember, the next size Slantfin was 145,000 BTU so we went with that. One little thing we forgot/missed was the stack effect. House was built in 1900 and , even though insulation was added, it leaks air like a sieve. The boiler runs fairly constantly and is maintaining inside temp at about 65-68 F so we are comfortable dressed a little lighter than you suggest although the Kitchen is cold because the radiator serving that room was removed decades ago. Stay warm, safe and have a happy New Year.

    • Yeah, jumping up to 145,000 Btus is too much. You bet you'll get the stack effect.

      I brushed up against that issue above in the column talking about using a furnace for the warehouse in your house.

      I've discovered it's so much better to keep it simple. Trying to explain Btu heat loss / gain, delta-T design differences, etc. causes the average homeowner's head to explode.

      TNX for the great story!

  5. Tim,

    You only mentioned one of the factors that helps us to "feel" comfortable in our homes. You need to add the role of humidity. I keep my house at 72 while I'm at home, but 72 in these below zero temperatures doesn't "feel" the same as 72 in spring. The key is getting the humidity right and that's difficult when the outside humidity is 10%. I try for an inside humidity of 50%, but my current humidifier can't keep up, so I feel cold. So I need to resize my humidifier or supplement it. My furnace runs a bit more than 75% of the time at sub-zero temperatures. I think that's size about right.

    Enjoy your articles!

  6. Tim -

    Another thing for folks with hot water heating systems to look at is the high/low setting on the furnace aquastat. My son and his family moved into a new house a year and a half ago. Last winter here on Long Island was cold, but not like what we're having now. They were complaining that their house was cold all of the time, so I went over to take a look. I felt the baseboards and they were warm, but not hot. After checking a few things out, I remembered the aquastat. Sure enough the high and low were both turned WAY down (high=120, low=100). Once I bumped it up to high=180 and low=140 the house became warm. I explained to them that they are now going to burn more oil, but at least my one year old granddaughter will be warm! ๐Ÿ™‚

    Keep up the great work!

  7. Several comments & questions:

    1) How much do storm doors help? I have 3 entry doors, but I haven't yet installed storm doors.

    2) I like cove heaters - like a baseboard only near the ceiling. Much cheaper that under-floor heat, and it warms the floor too.

    3) How do you keep out the cold from a range hood that's vented directly outside?

    4) Electric space heater safety tips: avoid extension cords, but if you have to use one temporarily, make sure it's sized for the load. Clean the dust out of the air intake area before the season starts. A clogged intake can cause the heater to draw more power and overload the circuit (possibly starting a fire if the cord and/or circuit weren't properly rated). Turn it off when you're not home.

    5) I wish I hadn't gotten windows with "low-E" coating. I have several big windows on the south side, and plain windows would have been wonderful for winter heating in the North - not to mention cheaper! In the summer, I could have just used reflective shades to keep the heat out.

  8. As Richard replied previously, it's quite important to introduce humidity into the warmed air from your furnace. Not only does it feel warmer, but your furniture and flooring will thank you. Ask a piano tuner what the effects of dry air has on a piano over time.

  9. We moved into our present house (about 110 years old) near the WI-IL border 27 years ago. For whatever reason, the supply line to our upstairs toilet tends to freeze whenever the outside temperature drops below 5 degrees F, but has never burst. I called our plumber yesterday & he told me to locate said pipe in the basement & place a small space heater under it where it starts its ascent to the 2nd floor. I was skeptical at 1st, but it worked! To be sure, it's not a final or perfect solution, but absolutely a temporary improvement. Obviously, you need to take precautions to keep the heater far enough away from flammable materials that you don't burn your house down & I accept no responsibility for YOUR results--but it worked for me!

  10. Tim, you have a great way of explaining this common problem so that it can be easily understood. Like you, I bundle up when it's extra cold; I also use a 'throw' when I'm at my desk or watching TV. Another thing I sometimes do is to warm my jammies & a pair of old loose socks in the dryer for 5 minutes +/- at night to help me relax & more easily fall asleep.

  11. Tim, Richard is right on the ball. A lot of us folks
    would feel much more comfortable in this very cold
    weather if we could boost our humidity level up
    from around 25% say to around 50% --A good low cost way: Try a Honeywell HCM-350 under $60.
    To check Humidity level use a Meade Humidity
    low cost gauge.

  12. We built a new home (and bed & breakfast) in the Upstate of SC about 6 years ago and installed geo-thermal. We put in two units with 2 air handlers to better control the temps between the upper level and the lower level. (Our B&B guests use the lower level.) I added a humidifier connected to the air handler to the upper unit since we also have a wood fire place on that level. Best decision ever! A wood fire place really dries the air! But, when the outside humidity drops down to 20% or so, there is no way we can set the inside humidity up to 50%. The bottoms of the windows and the window sills become very wet. I increase the setting as much as I can (because it does help us 'feel' warmer) but, I watch the windows for moisture and turn the setting down if needed. I also notice that the auxillary heat turns on in the lowest outside temps. Like heat pumps, the geothermal can only grab so much warmth from the ground and the 'electrical heat strips' are needed to give it extra umph.
    Thanks, Tim for a great email and informative articles.

  13. The Meade indoor/outdoor temp/humidity gauge
    MEADE- TM-005X-M around $32. is available
    from 'Weather-Shack" This is the best way by far
    to get accurate humidity/temperature readings period

  14. Happy New Year, Tim!
    Thanks for this great column - very appropriate and quite helpful. I'd love to hear your take on humidification - we have hot air heat and I long ago installed a central humidifier with humidistat. It does help, but I always worry about excess moisture which can condense inside walls, etc. and possibly cause mold problems. I try to manually adjust the humidity level; when it's really cold out and I start seeing condensation on the bottom of windows, I decrease the humidity. What advice do you have in this regard - and would you use a humidifier at all?
    Keep up the great work!

  15. The primary step is always to attend to heat loss which means looking at any air leaks and insulation. In Europe insulation standards have become so good that a single candle CAN maintain the temperature in a house that is kept closed. This is achieved by building slab on thick polystyrene insulation on the ground, use of thermal mass heat sinks, triple glazing and so on. The second point that strikes me is that central heating is a luxury. If temperatures are very low, it is highly expensive to heat a whole house when only one or two rooms are being occupied. It is cheaper to heat one room than a whole house, so if it is really cold pick a small room and heat it with a localised heater rather than cranking up the heating for the whole house. Also, the cost of heating is exponential, not linear. Every degree you increase the temperature adds more than you think to the cost of heating.

  16. Hi Tim great article, I was thinking about changing my heating system from fuel oil to propane since we don't have natural gas on my block. We run our stove, dryer, and fireplace with propane. Hot water heater and forced hot air furnace with fuel oil. We also use a pellet stove. Pretty crazy having all these different types of heating. What's your opinion.

    • You need to look at fuel costs for both. Oil requires LOTS of periodic maintenance as you need to change the nozzles at least every two years. Filters must be changed more often.

      Propane requires NO maintenance. It's like natural gas. Rarely does a burner need adjustment.

  17. The mentality that puts the ducts & furnace in the attic is a critical mistake. The entire apparatus gets temperature soaked ( wrong for the operation desired ). In the winter I can feel the cold soaked duct air blowing onto my bed for a long time. I would willingly pay for the extra sq footage to locate the unit in living space area & pay for ducts in the wall. UL once sensored up a house to study heat / gain loss & also the stack effect. Looks like it may be the next century before any of the knowledge gained will be widely implemented.

  18. Yep, I wonder too, why it's so darn cold and Furnace is running???
    But I just cranked it up couple #'s and it warms it up....but no time it's cold again....
    Can't wait till this cold weather is over..... I wear double layers at the top, and wear sweat shirt & sweat pants everyday, unless I go out then I wear my jeans....so don't want any more layers on, and could not stand hat & coat on inside.....
    I have electric blanket, I turn on about 10mins. before I go to bed, and turn it off before I get in the bed, and my heat is turned down and it does not come on at night at all...but when I get up, it's sure cold....but I like a cool room to sleep in tho....don't need any heat, once I get in bed.

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