Heat your home with a dehumidifier
2009-10-25 by Rob - Categories: Experiments, Home heatingA moisture problem
We (my wife and I that is) keep the temperature in our home relatively low in winter. As I’m writing this, it’s a balmy 16 degrees C in my living room. My lovely wife is wearing a toque and she’s about to put on another sweater because she’s feeling “a bit of a chill”, but she’s a trooper and wouldn’t have it any other way. That’s how she was raised. In Richmond, BC, where we live, winters are… well… wet. It’s pretty much a case of 100% relative humidity outside 24/7 and the water table is at ground level… well… truthfully sometimes it’s a few feet above ground level, but that’s why we have the pumps.
Combine 100% relative humidity outside with low temperatures inside and as you might expect, we occasionally have issues with condensation, especially on windows. “Experts” generally don’t recommend keeping interior temperatures below about 17 degrees C for exactly this reason. I don’t care much for expert opinions (experience has convinced me that I’m more expert than most of them), but I also don’t care much for condensation.
A solution with a bonus: free energy
The solution (without simply raising the temperature of our home), is a dehumidifier. While I purchased it for its intended purpose (to reduce humidity levels) I now realize that it also makes a very effective heater. Ah… but doesn’t it cost money and energy to operate a dehumidifier? Well… actually… NO! At least not in the winter, when we’re heating our home with electricity anyway. In fact, a dehumidifier is MORE efficient than an ordinary electric heater, which is already 100% efficient. Yes, a dehumidifier is more than 100% efficient at heating your home. That is to say the amount of heat a dehumidifier will release into your home is greater than the amount of electrical energy it will consume. The reason is simple: a dehumidifier removes energy from water vapor in the air in order to condense it to a liquid. This energy is released into your home.
It’s all about enthalpy
There is a property of any substance known as the enthalpy of vaporization. “Enthalpy” really just means energy. The enthalpy of vaporization of a substance is a measure of how much energy it takes to convert a given mass of the substance from a liquid to a gas. It also indicates how much energy is released when a given mass of the substance is condensed from a gas to a liquid. The enthalpy of vaporization of water is 2257 kJ/kg.
What is the efficiency?
How efficient is a dehumidifier at heating your home? Let’s figure it out together. I mean that literally. As I write this, I haven’t actually figured it out yet myself. I’m flying by the seat of my pants here, people; I’m a scientist gone rogue. But luckily I’m also a scientist who recently acquired a portable dehumidifier. I plugged it into a Kill-A-Watt meter several hours ago to measure exactly how much electrical energy (indicated in kWh by the Kill-A-Watt meter) it consumed. It’s been running for about 8 hours and it has consumed 3.87 kWh of electricity. Thus, based on the first law of thermodynamcis I know it has put at least 3.87 kWh of heat into my home.
However I have also determined with a simple digital scale that it has condensed 3.23 kg of water in that same time. How much additional energy did it release into my home as a result of that? That’s where the enthalpy of vaporization comes in. 3.23 kg multiplied by the enthalpy of vaporization of water (2257 kJ/kg) gives 7290 kJ of energy. A kWh is equivalent to 3600 kJ so 7290 kJ is equivalent to 2.025 kWh.
Thus, the total amount of heat released into my home by the dehumidifier over the last 8 hours is equivalent to the 3.87 kWh of electricity consumed, plus the 2.025 kWh of energy released by the condensation of water. The “efficiency” is equal to the energy output divided by the energy input or in this case (3.87 + 2.025)/3.87 = 1.52 or 152% efficiency. An efficiency over 100% is more appropriately referred to as a “coefficient of performance” since technically, it is impossible to achieve greater than 100% efficiency (having more than 100% efficiency in energy conversion would defy the first law of thermodynamics). So if you ever measure more than 100% efficiency, as I just did, what it really means is that you have moved energy from one place to another rather than simply converted energy from one form to another. Such is the case with a dehumidifier which removes energy from water vapor and releases it into the home in the form of heat, condensing the water to liquid in the process. But whatever the terminology you want to use, the fact remains that I can release 1.52 kWh of heat into my home for every 1 kWh of electricity my dehumidifier consumes.
What’s the payback time?
I paid about $250 CAD for my dehumidifier. It consumes about 480W of electricity (3.87 kWh in 8 h) and outputs about 730W of heat (480W*1.52) into my home. I can buy a decent electric heater that will output 730W for about $50. So the difference in price is about $200. Let’s calculate the difference in the cost to operate. A 730W electric heater consumes exactly 730W of electricity. The dehumidifier only consumes 480W of electricity to produce the same 730W of heat. The difference (730-480) is 250W. Effectively I get a free kWh (1000 Wh)of heat for every 4 hours of operation. I currently pay about $0.07 per kWh for electricty, so I save about $0.42 per day when operating the dehumidifier in place of a heater. My heating season runs from October through March, or around 180 days of the year. Therefore, I can save about 180*$0.42 = $75 per year by operating the dehumidifier in place of a heater. That will take a little over 2.5 years to pay back the difference in price of $200.
Will this work for anyone?
In a word, “No”. The human body is most comfortable at a relative humidity between 20% and 60%. I can run my dehumidifier continuously in winter and not expect to ever drop below 20% relative humidity inside my home. The same may not be true for homeowners in other locations maintaining their homes at higher temperatures than I do. Heating with a dehumidifier works for me because of the high relative humidity in Richmond, even in the winter, and because of the low temperature at which I keep the interior of my home. It could work well for anyone who lives in a similar environment and keeps their home at a low temperature. But if you live where temperatures are usually below 0 degrees C outside in winter then you likely have a much lower relatively humidity. In that case, a dehumidifier will not be able to condense nearly as much water for a given amount of input energy and its operation may bring the relative humidity below a comfortable level.
Clothes dryer vs a rack and a dehumidifier
If you’re considering hanging your wet clothing to dry inside your home, vs using your drier, then you should know that a dehumidifier will be far more efficient than a clothes dryer. In the case of a clothes dryer, electrical energy is used to vaporize the water in your clothing and the water vapor (and all the energy you’ve put into it) is expelled from your home through your drier vent. There is a net loss of energy from your home. If instead you use a dehumidifier, the heat already in your home is used to vaporize (evaporate) the water in your clothing. This energy is recaptured by the dehumidifier when the water vapor is condensed to liquid. Unlike the drier, the dehumidifier doesn’t expel any energy from your home.
Heat pump vs dehumidifier
A dehumidifier is effectively a heat pump. Rather than extracting heat from the ground or the outside air, a dehumidifier extracts heat from water vapor contained in a home’s inside air. In my home, for reasons given above, I can run my dehumidifier continuously without reducing the relative humidity in my home below a comfortable level and I’ve found the coefficient of performance (COP) is about 1.52. A typical air source heat pump has a COP of around 4 assuming an outside temperature of around 0 degrees C (a typical Richmond winter). A typical ground source heat pump has a COP of around 7 assuming a ground temperature of around 10 degrees C (a typical Richmond ground temperature). So clearly, a heat pump (either air or ground source) is much more efficient. If I had a heat pump, I would be consuming more energy than otherwise by operating my dehumidifier. That said, I feel secure in the knowledge that I can run my single dehumidifier continously and consume less energy to heat my home than if I were running an electric heater. I’ll save the installation of a heat pump for another day… perhaps.
Can you heat your whole home this way?
No. If I were to install more portable dehumidifiers to provide all the heat my home requires (to maintain a balmy 16 degrees C all winter long) I would almost certainly bring the relative humidity below comfortable levels, and the COP would drop below the measured value of 1.52 simply because there isn’t enough water vapor in the air to be condensed. So the idea of using a dehumidifier to heat one’s home is clearly not scalable. At best a dehumidifier may provide suplemental heat. I think I might get away with using two portable dehumidifiers continuously which would each save me about $75 per year based on the calculations above. That’s about $150 per year in total. Currently, that’s about 10% of my home’s annual heating bill.
Hi Rob,
Thanks for the math and your insight on humidifiers as heaters.
If an air conditioner were turned around so the coils are indoors and the air intake/output are to the outside,
and a small fan blew air across the coils (now to the inside), would this would as a mini air heat pump and
if so what do you estimate the heating savings to be?
thanks.
Thankyou for the post… As you might have seen from my comment(s) on your oil filled heater project, I heat my house with electric power. There is one area that just gets what it can from whatever is running and that is downstairs. Last year I just dropped a space heater (small hot air burning element with fan in it) in the middle and ran it often at the full 1500w. We kept it at about 17C, I haven’t set it up yet this year and so it is only 15.6C down here right now
anyway, there is more water in the air down here too (shower, laundry etc.) and so this may be a great place to try it. 700 and some odd watts may not be enough for 400 sq ft…. but then again running all the time it might.
Len
Hi Ian,
I think a reversed air conditioner may work. I’ve been considering experimenting with that as well. My primary concern would be that air conditioners are designed for a different temperature range. They are designed for pumping heat out of air at around 20-25 degrees C and into air at around 30 degrees C and up. I don’t know how well they will function pumping heat out of air at around 0 degrees C or lower. I imagine there would be frost buildup on the outside. Above 0 degrees C you could simply turn the unit off periodically and allow the frost to melt, but below 0 degrees C you may need to bring the air conditioner entirely inside frequently to defrost it. I believe air-source heat pumps designed for home heating have built in defrost cycles (which incidentally is one reason that they are less efficient than ground-source heat pumps that don’t require defrosting periodically). Portable air conditioners are unlikely to incorporate a defrost cycle since they are designed for use at temperatures well above freezing. This is all just hypothesis on my part though. I think it would be a worthwhile experiment.
Hi Len,
It sounds like you may have perfect conditions for using a dehumidifier as an effective heater. If you try it, I’d love to hear how it works out for you.
Rob
Hi Rob,
May I just pick your brains a moment. We have a dampness problem in our guest room which is in the cellar. Water vapour generated by the ensuite shower room is condensing in the unheated guest room and condensing on the floor and seeping into the laminate flooring. So we need to get rid of this water vapoour. I want to do it the most energy efficient way.
I know dehumidifiers are great (I’m a chemist and love to rave about the benefits to the world of hydrogen bonding without which the humble water molecule could not generate so much energy just by condensing … oh heck while I’m at it did you know that rain in the UK generates the equivalent energy output per year as 1.3 million power stations which is one way we avoid your Richmond winter climates). Anyway back to the question.
Is is better to run a dehumidifier or a extractor fan or just leave the window open to remove the excess water vapour.
Dehumidifier runs a higher wattage solves the dampness but warms a room we don’t always need warming.
A humidity sensitive extractor fan runs lower wattage but presumably takes longer to remove dampness.
Leaving the window will only work if the water remains vapour and so presumably requires the room to be heated – and it relies on the outside humidity to be less than the inside.
Any thoughts
Adrian
Hi Adrian, your guess is as good as mine. All methods you described may work, but which method will result in the least energy consumption is difficult to say since there is no way to know how long each method would need to be active in order to be effective. I think trial and error is the only way you will know for sure.
Hi Adrian,
I’m no expert. My thoughts are do all of the following:
1. If the shower stall backs to an exterior wall – put in window on the wall towards the top of the ceiling to be left open while showering.
2. put in a fan in the ceiling that you can run while showering.
3. Get 2 boxes of deliquiescent (sp?) and put one in the room with condensation while the other is losing moisture when you set it outside.
Ian
Hello!
I don`t understand one thing about payback time. How did you save $0,42 per day? You said “effectively I get a free kWh (1000 Wh)of heat for every 4 hours of operation”. That means 2kWh for free per 8 hours. And that is 0,07 * 2 = $0,14 per day. Where is my fault?
Hi Andris,
Sorry I did not make that clearer. 8 hours is just how long I ran the dehumidifier for my test. If I ran the dehumidifier continuously (24 hours per day) I would get 6kWh for free per day. And that is $0.07 * 6 = $0.42.
The de-humidifier was the final piece to the puzzle. I live in the Fraser Valley in a forty plus year old BC Box. I was trying to use portable electric heaters exclusively. By November 10 my house was damp, smelly and cold; we have old plumbing and our main bathroom does not have a fan so we have accumulated moisture. My son sleeps and spends most of his time downstairs, he was uncomfortable. My husband and son were quickly loosing resolve.
I found three very inexpensive 30 litre dehumidifiers. I have used them full power for the last couple weeks; one upstairs and two downstairs. I don’t remember my house ever being this comfortable.
Thanks for all you work
Mary
Hi…this is my problem…we installed a heat pump with 4 heads..(none in the basement)the good news is our furnace has not been on..the bad news is our basement is freezing..15c ( and warm (very) in the summer) and because we have no heat from the furnace it is humid and warm in the summer …so my thought is that the dehumidifer would most likely be a solution…any thoughts!!
Hi Vicki,
I’m not entirely sure what your question is. Yes, a dehumidifier will make your home less humid. It’s particularly good if you live in an area that is more humid in the winter, since the dehumidifier also produces useful heat (making it essentially free to operate). Using it in the summer it will still help your humidity problem, but it will also make your home hotter, and the operating cost will be higher.
Hi Rob,
I don’t want to rain on your parade….but. A dehumidifier does not put heat equal to the kw used.
The dehumidifier does useful work from the kw ie: motors for the compressor and fan, they are not 100% efficient, so the only heat from the kw is that amount between useful work and 100%. Typically an electric motor will be some where between 50 and 90% efficient, the compressor like wise isn’t 100% efficient, so the only heat is the delta of efficiency. Heat is only generated in the delta, in other words if you were generating 100% heat from the kw you would have heating elements, if all kw went to heat the motors, fans and compressor would not run.
Lloyd
Lloyd,
You seem to be suggesting that the energy disappears after being converted to work? That defies the law of conservation of energy (see http://en.wikipedia.org/wiki/Conservation_of_energy). If a motor is 80% efficient then 20% of the input energy will be converted to heat in the motor. The other 80% will do useful work, yes, but unless that useful work results in energy storage (for example, raising a mass, stretching a spring or charging a battery) the energy will eventually be converted to heat. It is a requirement of the law of conservation of energy.
For a simple example, consider an electric fan. If the motor is 80% efficient (actually fan motors are typically very inefficient), then 20% of the input electrical energy is converted to heat in the motor. The other 80% does “useful work” meaning it is transmitted through the motor shaft in the form of torque and angular displacement. This useful work will be converted to heat at the interface of the fan blades with the air (similar to how the space shuttle heats up moving through earth’s atmosphere only on a much smaller scale) or in the air itself (due to turbulence induced by the fan) or at another surface that the air hits. When you turn the fan off and the air stops moving, there is no more work. It has all been converted to heat.
The operation of the motor, compressor and fan inside a dehumidifier is more complicated but there is no need to consider the details. The law of conservation of energy requires that unless energy is stored, any work done must produce heat exactly equal to the amount of work done.
In other words, for most electrical appliances that operate inside your building envelope, the heat input into your home is exactly equal to the electrical energy consumed, regardless of any work done. A 200W fan will put exactly the same amount of heat into your home (200W) as a 200W heater. A dehumidifier is a special case since heat is output both from the electrical consumption and from the condensation of the water.
Rob
I used to own a dehumidifier but found that mine would not work at temperatures below 68 degrees without freezing up. We don’t keep our home warm enough for proper operation. It also was far from quiet, so it’s operation produced annoying noise pollution. Does anyone know of a truly quiet unit that operates well at colder temperatures? Thanks
Hi Rob,
This is a nice piece of measurement and analysis, and I believe your general conclusion. However there are two flaws.
1) Much more water vapour would have condensed onto the interior walls and furnishings, thus generating energy of condensation, if you had not used the dehumifier (that is, after all, why you bought the dehumifier). The heating gain you calculate ignores the fact that this condensation no longer occurs.
2) Sound, light and electro-magnetic radition emitted from the dehumifier can escape the house without being converted to interior heat, so the electrical energy used by the device isn’t all used to heat the house. Even when trapped by the walls, these forms of energy will distribute heat around the perimeter of the space, where they can be lost more quickly.
My guess is that 2) leads to a relatively small correction, but 1) probably has a more serious impact.
Cheers,
Mark L
PJ, some dehumidifiers have freeze protection; they either pause or run a heater when their coils get too cold. Dunno about noise, though; that doesn’t seem to be a big priority.
Rob, you can add condenser clothes dryers to your list; they’re basically dehumidifiers. Bosch is one vendor.
Dehumidifier bonus: dry air feels subjectively warmer (when it’s cold, that is).
Mark L,
Most of the condensation you mention in your first point is perimeter condensation anyway. In my experience of cold housing I would expect most condensation to occur on the (relatively) colder windows in comparison to the walls and/or interior furnishings. As the R values of windows are much lower than walls I’d have thought this isn’t the best place for it to be released if making use of the heat is a concern. Wouldn’t having it released within the dehumidifier allow for better use of the heat output compared to just using it to temporarily speed up the molecules in the glass of my super-low-R-value window panes?
Cheers,
Steve
Steve> Most of the condensation you mention in your first point is perimeter condensation
That’s true, but now we’re talking about the distribution of heat, in which case we need to consider the thermal characteristics of the space being heated. Rob’s original calculation ignored distribution and simply counted all the heat of condensation from the dehumidifer and all the electrical energy as “delivered” heating in some sense. This overstates the coefficient of performance, and in many cases the overstatement would be significant.
Cheers,
Mark L
Hi Mark,
I read your arguments with interest. Thanks for posting. While I agree with the principles you describe, I think the magnitude of their effect is relatively low (at least in my case).
When not using a dehumidifier, we notice condensation only when we add moisture to the interior air by having showers or cooking or hanging wet laundry, etc. This “natural condensation” is a tiny amount compared to that induced by the dehumidifier. Also, natural condensation may result in water condensing on walls, windows and such during periods of high internal humidity but this water will evaporate into the home again over time. Unless there is a net accumulation of liquid water, the net heat released into the home is 0. Natural condensation does not result in a net accumulation of liquid water (not in our home, anyway). The dehumidifier on the other hand results in a net accumulation of nearly 10 litres of liquid water per day which is removed from the home in liquid form resulting in a positive net heat release into the home.
There is a third “flaw” in the above calculation. I ignored the heat removed from the liquid water after condensation. When the condensed water drips into the dehumidifier reservoir it is just above 0 degrees C. If removed from the home before it warms up (using the dehumidifier’s drain tube), there is additional heat input into the home. How much? Suppose the condensed water results is 15 degrees C below ambient. The specific heat capacity of water is about 4 kJ/kg/degreeC. Cooling 3.23kg of water by 15 degrees C releases an additional 194 kJ of heat. You can see why I didn’t feel obliged to mention this. Compared to the 7290 kJ of heat released from condensing the water, the additional 194 kJ from further cooling the water releases only about 2-3% more heat into the home. I think the effects you described may be about the same magnitude only in the opposite direction so perhaps they roughly cancel.
I do agree with you that my “original calculation ignored distribution”. Heating spaces that don’t need to be heated isn’t efficient (especially perimeter spaces). Unfortunately it’s exactly these cooler spaces where people may be tempted to use a dehumidifier to prevent condensation. I prefer to think of my dehumidifier as an electric heater and locate it accordingly.
Rob
Mark, is it not possible that the humidity could just stay at (say) 70% if the dehumidifier is not running, without much natural condensation? I would have thought that any water that condenses onto (say) a sofa would just evaporate again – there’d would be some stable “sofa dampness” (at any given air humidity).
One problem with using a dehumidifier for heating may be using up the available humidity – or too much of it. A friend in Stockholm says that she really needs a humidifier, as her apartment is uncomfortably dry.
Ok, I was confused. It’s not “condensation that would have happened anyway” that’s the problem, it’s the extra evaporation from environmental surfaces that happens when the air humidity drops.
So if 2 litres of water end up in the dehumidifier, that may drop the water content of the air by 1 litre and the water content of various surfaces by 1 litre (a net 1 litre condensation) rather than dropping the air water content by 2 litres (for 2 litres of condensation).
However I’m not convinced that the furniture and walls will hold that much extra water if the air is at RH 70% than at 60% (which is about what I get from taking 2 litres out of a large room or group of smaller rooms). And if you push the RH much below 60% – and certainly below 50% – it starts getting uncomfortably dry.
Hi Rob
Like all others that visit, I enjoy your website and ideas. We’re up in North Vancouver. My wife also wears multiple sweaters indoors, but would divorse if she had to resort to touques!
We have just finished installing a high efficiency water to air heat pump and HRV system at our coastal cottage (heat pump COP 5ish). We also completed a fairly significant insulation, window, and sealing upgrade.
When un-occupied we keep the temp low at 12C and noticed some mold on artwork. I found your website researching dehumidifiers and agree with your COP of 1.5 for dehumidifier heating. But it now leads to the next question.
Is it more energy efficient to control moisture and mold with heat pump heat at COP of 5 or with the dehumidier at COP of 1.5? or a combination? I can theorize how to evaluate this, but my background in this area is relatively limited and I’m not sure I’d select appropriate operating conditions to compare. I’ll probably resort to experimentation with a $200 humidifier.
Could I trouble you for your thoughts on this?
Also we researched the enerstar dehumidifier listing and found the 25liters /day sizes were all in about the 1.6 liters/kWhr energy efficiency. The larger they got the more efficient they got. Are there other types of dehumidifiers that operate at significantly higher efficiencies we should be considering?
Thanks again
John
Hi John. The answer is it depends on the cottage
. You need to know how many watts it takes to raise the cottage temperature by one degree C. My home (2500 square feet, reasonably insulated), for example, takes about 200W per degree C. If your cottage is similar then your heat pump would draw 1/5th of that or 40W per degree C. Perhaps you need to get the temperature from 12 degrees C up to around 17 to reduce mold. That would require a 200W draw from the heat pump. I bet you could achieve a similar effect by running a 500W dehumidifier on a timer so that it only runs 1/4 of the time (125W average). So I think it’s likely that the dehumidifier would be cheaper. Again… all guesswork.
I’m no expert on dehumidifier brands or efficiencies so I can’t help you there. All I did was test the one I bought.
Excellent analysis and responses – there seems to be very little info out there regarding the impact and economy of using dehumidifiers in the home.
This sounds great for dehumidifiers that make use of a refrigerant and condenser. What about the other domestic dehumidifiers that use desiccant and rotor technology ? I am thinking of buying one of these , but this blog post has caused me to pause.
From what I understand (very limited) the silica gel in these systems absorb the water molecules in the air which is then sweated off with a heat source and eventually collected. Would I be correct in assuming that this type of technology would be inferior to the condenser type with regards to generating “bonus heat” ? or do the desiccant systems generate bonus heat via some other process ?
Thanks
Al
Hi Alan,
I don’t know much about desiccant based dehumidifiers, but the law of conservation of energy effectively states that the process by which condensation occurs is irrelevant. If you start with water vapor and end with liquid water, then you will have released a certain amount of energy. If there is no form of energy storage in the system, then that energy will be released in the form of heat. Thus all dehumidifiers will release “bonus heat”. However, their coefficient of performance (ie how much heat energy out per unit of electrical energy in) may vary. Without actually testing, I don’t know what type would have a higher COP.
Thanks for clearing that up Rob…
Hi Rob:
Our laundry machines are located in an alcove just off the side of our open kitchen-dining area & our main source of heat for the entire home is electric baseboard. I’ve installed a wood burning stove & do try to have it working through most all of the colder seasons to prevent having to use the electric heat.
I’ve even gone as far as disconecting our dryer’s electrical supply because it was constantly being used for undersized loads, while my daughters lived at home & installed a clothes line at the back deck for all laundry drying.
Since they’ve moved on, we still now, just use the clothes line to dry laundry but because of our age & the convenience of having a dryer, I’m hooking it back up soon.
My thoughts were, to vent the dryer directly into a de-humidifier & release the expelled heat into that arae of the home, while capturing the moisture content, instead of waisting even more energy by venting it directly outside. Is this possible using typical residential use de-humidifiers?
Hi Rob
Thanks for the feedback.
We purchased a small Enerstar dehumidifier about $120 on sale at Canadian Tire. I believe it is only 60W of power demand and operate it full time in the unimproved basement of our cottage. The basement is now remarkably warmer and enjoyably dryer. It removes about 1.5 liters of water a day. Intuitively I believe the warm dry basement is contributing to a warmer dryer home, reduced mold potential and probably increases the heat pump efficiency not having to heat moisture laden air.
I haven’t attempted any power comparison with the heat pump, but given the heat pump compressor is 2-3 kW depending on speed, we seem to have achieved significant benefits at a fraction of the heat pump’s power consumption. The dehumidifier is noisy due to high airflow noise but in the basement one barely notices it.
We’re planning a similar basement installation in North Vancouver. We also plan to experiment with an indoor clothes drying rack in the same room as dehumidifier. Rusty who commented above about clothes drying might be interested to know that in Europe one can buy clothes dryers that operate strictly on dehumidification and I believe they exhaust into the building area.
Hi Rusty,
That would work, but depending how humid your house is to start with, you may find the drier dumps moisture into your home faster than the dehumidifier can remove it, and you may get condensation on windows and walls. Another option is to hang your wet clothing on an indoor rack and run the dehumidifier next to it. That’s what we do. I can’t recall the last time we used our drier.
Excellet site and wanderful comments from all. We do need this type of info much more. I have been doing these recommendations since first I bought my old house here in Vancouver 3 years ago. It’s a 60 year old cottage style one story house and I basically paid for the land. I first double glazed the old wood windows with 1/16″ clear plastic glass sheets, resurfaced the floor with used but nice wood floor with good underlay and do use a dehumidifier since beginning. I totally disconnected myself from gas company and pay average 50$ a month for my electricity which is used for everything. I have slowly reduced the temperature inside from 20 to 18 and this year to less than 15 degrees all winter. I use only one small electric heater which is one of those with fake fire display and more importantly it is a mobile one. So we, My wife and I, actually move it when it is needed, though most of the time it is located in the living room. To reduce the consumption we do turn it off during sleep and during day when we are at work. So it is basically used a few hours of evening when we are home. That means inside temperature fluctuates between 16 to 12 during night when temperatur falls. But it really doesnt’ bother us and actually feels great to snug in. One trick we use, which we have learned from our cultural background in middle east is to use a large bed spread to put on top of the heater and sit around it by using it to keep our lower body actually it sometimes even hoter than we can handle:) This is a great trick, because the heating area has been step-wised in the sense that where we are sitting it is above 20 degrees, and as you get farther in the living room it gradients out to 15.
I like it that you do bring up this very important point in responding to people comments about how much efficiency of various electric appliances is not important, as long as, they are contributing to heating useful space. This is another one of gimmicks of these industries to sell us new appliances in the name of “Star” rated!! In an area like BC we really do not need to go out and replace a perfectly fine apliance in the name energy efficiency. Sure, if you need to buy one, well, better buy an efficient one since it may be put in a “wrong” place. But we should really more emphasize on locating these electric appliances somewhere they can contribute to our heating rather than spend top money for saving a few $ a year on energy on that appliance. When one think of this way, in fact having a regular ( and not a “STAR” rated one) is actually a benefit! why? because they usually are not located all in the same spot in the house and so they contribute to distribution of heat.
As a side note, I just received a letter from Fortis BC, the new owner of Terason Gas, that they are basically threatening, politely of couse, to disconnect my gas meter if I don’t activate it again! Of course in the name of safety!! These sleezy business practices really is outrages. What had from very beginning turned me off on gas is the running fees they would charge you for just previlage of having the option of using it! And consider that gas price has been kept depressed in the market as long as I remember, but not for the consumer. So, no, thanks you. I prefer to pay my hard earned money to BC hydro, at least it is not polluting the environment as much.
Thanks and keep up the good site.
Thanks for this info. I also keep most of my house very cool. But with the dehumidifier running I get about a 3 degree rise in my bedroom. And since I work the night shift the hum of the dehumidifier blocks out other noise. So this was definitely a winning solution for me.
you cant gain heat from a closed system and your house is just that. the only heat gain is coming from the transmission line that is outside of the system and it is powering your dehumidifier. the humid air is already inside the house.
Hi JohnC. I agree that a house can be treated as a closed system. Standard practice in thermodynamic problem solving is to identify the closed system and identify mass and energy transfer mechanisms into and out of the system. It may be true that the transmission line is the only direct energy transfer into the home (excluding solar radiation), but there is mass transfer into and out of the closed system in the form or air infiltration. If that were not the case you would quickly exhaust all the oxygen in your home and suffocate. The amount of air infiltration is much more significant than you might imagine (typical minimum recommendation is 3 to 4 air changes per hour and houses that are sealed well still need to provide that using ventilation fans). If the temperature of the outgoing air is higher than the temperature of the incoming air, then I’m sure you would agree that represents a form of heat loss from the home. Likewise, if you condense water from the incoming air resulting in drier outgoing air plus outgoing liquid water (poured down the drain), then that represents a form of heat gain within the home. The amount of heat gained is simply the heat of vaporization of the water.
Hi Rob, Sounds like a great way to cool a house and keep it dry, but as far as gaining heat from cool moist air that enters the house through cracks and the like, your just bringing in cool moist air then heating it to room temperature removing the moisture and releasing it back out of the building along with the heat gain that was added from the building. Also you will be dumping a percentage of that heat down the drain.
@ JohnC, I appreciate your persistence. But compare the two scenarios:
1. Without dehumidifier: cool moist air enters the home and room temperature moist air exits the home.
2. With dehumidifier: cool moist air enters the home and room temperature dry air plus liquid water exits the home.
In both scenarios the air and water vapor coming into the home contain the same amount of energy (I think we agree on that). But in Scenario 2, the air and liquid water exiting the home contain less energy than the air and water vapor exiting the home in Scenario 1 (I’m not sure we agree on that… if not, look up “enthalpy of condensation” in wikipedia). Since Scenario 2 has less energy loss from the home, where do you suppose the “saved” energy goes? The first law of thermodynamics says energy must be conserved. The answer is that the energy (the enthalpy of condensation) is released inside the home in the form of heat.