Heat Circulation for House

Something to consider: Floor vents have fallen out of favor because they allow fires to rapidly escalate upwards between floors. Something as simple as a laundry chute is required to be metal lined or ductwork under some fire codes. In-floor poly tubing has become a more popular method of heating floors but is labor intensive.

Good call recycledscience. Any floor penetration would require a fire damper be installed in the opening.

What is your current heating system in the house? Forced Hot water?

Sorry, I forgot to mention that it's a forced hot air system.

I have ever seen people heating houses, and specially its floors, by the use of a closed loop of water comming from a reservoir over a stove or even in the back of a fireplace and circulating by natural convection in ducts installed just below the floor panels (expensive to install if not expected at the design of the house). Some systems use radiators (less complicated, you must route tubes although and install radiators along the way). This is an ancient way of doing, but still safe.

If there's no problem with circulating air between floors, I would not worry about the cold air return. Convection is powerfull. If you find a way to direct warm air up, the cold air is comming down through corridors and stairs (keep doors opened...)

By the way, have you considered installing a second glass in the windows? Is your roof well insulated? Those are great energy loss items.

Hello, thanks for your input.

The top floor is a walkup type attic with the remaining portion of the roof, a 4-5' high crawl space. The crawl space has blown in insulation. The eves in the rooms may or may not be. But when you tap on them, they do sound muffled. I have R-30 insulation to install over the blown in. I read out a product that when added to laytex paint it creates a reflective barrier on both sides. I was thinking of painting the walls and ceilings with it.

Thanks,

Brian

An interesting approach would be to get some heat recovery from your pellet stove stack (flue) using a hot water coil and small circulator. The coil would be wrapped around the stack running water through it with a small hot water storage tank to give you some mass. This could provide some heat to a small coil located in your supply air duct to the hot air furnace, locking out the furnace using a ac/heating thermostat running it on fan only. The only problem would be cool stack temperatures from the pellet stove possibly causing some condensing in the stack causing it to rot out early. Just a though for your situation. We are registered in N.H. if you need drawings. lol!

Wonder if cooling flue gas too much by hot water coil would hinder efficient venting, possibly leading to pollution of basement atmosphere? Depends on height of flue terminal. A Carbon Monoxide detector would not go amiss here.

Cool stack temperatures are not good unless you have a system made for it. A condensing boiler is high efficient, uses stainless steel venting due to the moisture created. The moisture has a PH level of 4 which is acidic. The heat exchanger would have to also be made of stainless to handle the condensate. Condensing boilers thrive on low return water temperatures and the lower the temperature the higher the efficiency. When you start your car in the morning, you see water dripping from the exhaust pipe. This will continue until the coolant temperature reaches 140 degrees. Above 140 degrees condensing stops. My thought for him was a coil wrapped around the stack of the pellet stove. You would insulate the coil using it as a heat exchanger to heat the water. The problem is water capacity of the coil. To solve the problem, a hot water storage tank would be needed, not only to give the system some mass, but to have a supply of water recirculated and used for heating of the hot water coil placed in the supply air discharge of the hot air furnace. Locking out the furnace and running fan only is only a thermostat change with some wiring to the furnace. Another way to get hot water for heating is using the domestic water from your hot water heater. This water can be used for heating also and is an easier solution than reclaiming heat off the stack. The advantage of using the heat off the stack is the pellets cost less than gas or oil. New Hampshire would be a great place to do waste oil heating, and my firm offers burner replacements or conversions for large institutions that want to run waste oil. It's alot cheaper than #2 oil.

Having only ever used the metric system I find something confusing. You mentioned that your stove was a 68K BTU stove, but a BTU is a measure of energy and to measure the output of a stove you need to measure it over time. My question is therefore over what period can you stove output 64H BTU, is this as I assume the output over an hour?

Hello Masu. Yes, it is per hour or usually seen in this situation as btuh.

Hey masu, the BTU is the standard power unit of measure for air conditioning (I think it's from UK). It's normally read as per hour, unless noted.

By the way, 68000 btu would be enough to heat 5 to 7 bedrooms, depending on the insulation and external temperature.

For reference, it corresponds to approx. 0,2928W in inteligible units .

Thanks guys I was pretty sure that's what was meant, but you never know with imperial weights and measures, it can be very subjective.

By the way I plugged 1 BTU/Hr into a conversion calculator and got 216.2 mw but when I converted BTU to joules and divided by 3,600 seconds the figure agreed with yours at 293 mw.

I really hate the imperial weights and measures, of late just about every time I have seen them used confusion reigns. I am going to stick with SI units in multiples of 1,000, you always know where you stand that way.

Every now then we will get a SI job over in the U.K. It's usually a hospital. I'm very familiar with using SI, because after you use it day after day, use tend to memorize the conversions and it makes life alittle easier, and the job moves faster. At first there is always some inefficiency until people get back up to speed.

The bottom line is your house is cold. Bite the bullet and put in double or triple glazed insulated windows. There are all sorts of treatments to make them look as ancient as your house. If you want to live by 1881 standards, buy more sweaters. They didn't have forced air heating in 1881. You are spending all sorts of money very inefficiently. The greatest return on your heating investment dollar would be new windows. All the insulation in the world applied to your atic and stone walls will not come close to the savings you will obtain by replacing your very inefficient windows. Money is tight? Well do a few at a time. I know you will miss that nice build up of ice on the inside of your windows from frozen condensation.

This is what we do here in the U.S. as Hvac Engineers

British thermal unit (btu) The amount of heat needed to raise 1 lb. of water one degree in farenheit.

A house built in 1881 would have a heat loss in the vacinity of 40 btu/sq.ft. This 68,000 btu or 68MBH pellet stove would have the ability to heat a house that is 1,700 sq.ft. with this type of resistence.

The calculation for heat loss is Resistance "R" value /1 = U value

U x A (Area per square ft. of wall) x Delta T (difference in temperature inside (72 degrees) - (Temperature outside N.H. use 0 degrees.) Glass and doors are figured the same way, but have infiltration of air per linear foot in cfm. Roof heat loss is figured the same way as the wall. There are other factors such as: Above a heated or unheated space, slab loss etc.

If this was a 68,000 btuh boiler pumping hot water with a 160 degree entering and 180 degree leaving water temperature, it would take 6.8 gpm of water circulated.

If he wanted to put a blower on this pellet stove, the sizing of the fan would be critical. You can't maintain 72 degrees indoor temperature with 72 degree air, so the leaving air temperature should be around 95 degrees to maintain 72.

Here is the fan sizing calculation based on 68,000 btuh.

68,000 BTUH / 1.08 (K) fan leaving air temp. (LAT) 95 degrees - fan entering temp. (EAT) 68 degrees = 2,331 cfm

The problem is that the output of the stove may vary with a 68MBH output at full load. The only way to correct this would be to install a variable speed fan with a duct mounted discharge temp. sensor set for 95 degrees.

Try to duct your heated air. Avoid cutting vents in the floors as you suggested. Our old house in North Dakota was similar in dimensions to yours with vents from room to room as you propose. The heated air flow was weak and dependent on leaving the room's doors open. Also interconnecting room vents eliminated acoustic privacy. My brothers and I spent many nights giggling at the sounds of our parents engaging in adult behavior LOL. A correctly sized blower assures equal air delivery to all rooms and would muffle and blend sounds providing acoustic privacy. Do continue investigating additional insulation schemes such as triple pane windows, urethane foam insulation, insulated doors and electric heating. A major advantage of electric heat is all the heat generated is used to heat the house. No heat is lost through a vent to the outside as in gas, wood and coal fueled heaters. Of course fireplaces are the least efficient method of heating however they, brandy, and Strauss are certainly conducive to romance.

I have retrofitted old houses with wood stoves and wood pellet stoves. (I am also too lazy to sign in...grin!) The old guys knew what they were doing when they sent non insulated chimney pipes through the upstairs bedrooms. Don't try to take too much energy out the chimney...you could mess up the draw. Most old houses have an air circulation plan...hot air from the kitchen goes up the back star, down the hall, then comes back down the front stairs...that sort of thing. Learn it, and use it. It works! Vents over the doors work a treat. Heavy quilts in cold rooms are just perfect. Building codes are vital for safety... get a permit. A warm floor is wonderful.

Email me if you want to chat futher.

stag@cyberus.ca

Good point about the draw. Cold air in the stack is heavy and will sit there, you are absolutely correct.

Here are a couple of suggestions. 1) Your original windows are probably single glazed. If so, kits are available to add plastic over the windows on the inside, which will reduce the heat loss through the windows. 2) I would suggest installing the pellet furnace in series with and ahead of your present oil furnace. The filter section would be on the return air side of the pellet furnace. Your pellet furnace would be set to be the primary source of your heat, such that when you needed more heat than the pellet furnace could produce, your regular furnace would kick in. You would set the blowers to run simultaneously, unless the pellet furnace blower had the capacity to produce the proper cfm to blow through both furnaces, and adjust their speed to produce the required cfm. Cut into the existing supply and return ducts in the basement, and add a supply register and return air grille in the basement . You would need a 2-stage thermostat to properly sequence the two furnaces, plus the usual high limit controls. Also, make sure the existing flue is large enough to handle both the oil and pellet furnaces. If not, you would need to add a separate flue for the pellet furnace. The temperature of the flue gases should be around 350 - 375 deg F to keep from condensing the flue gases, so don't try to extract heat from the flues by using pipe coiled around them. Use the existing duct work, don't add floor grilles.

You may find that the reflective barrier doesn't work as well as expected. Think about adding furr strips on the walls and install 1/2 inch urethane 4x8 insulating boards. They have an R rating of about 2.

.........Good luck, stay warm and save money!!

A domestic heating installation on forced hot water is shortly to be re-plumbed so that the solid fuel stove is the "duty" and the heating oil boiler is the "standby", thereby making the best use of the low-controllability carbon-neutral fuel (logs and scrap wood) for economical reasons. When the "duty" supplied insufficient or zero heat, the "standby" takes over.

Can the principle be applied to this particular poster's application?

Are you asking "can a solid fuel stove be inserted into the hot water system to produce hot water?" It can, if the stove is designed for that purpose. If it is just a stove or heater, then I would say that no, it couldn't. The combustion chamber wasn't designed to contain coils or other devices to extract the heat. The stove was designed to radiate its heat to the surface of the combustion chamber. Remember the flue gases should remain in the 350 deg F range. If its purpose is to take the chill off the air and thus delaying the operation of your boiler, you might consider leaving the hot water system as is, bringing it on as required to maintain your level of comfort.

If the stove can produce hot water, then you could certainly install it in the system with the existing boiler. I think in this instance it would be best to parallel the stove with the boiler, with it being your primary source. Nothing in the piping would change except adding the stove system.

There are several items which must be considered should you care to pursue this system. I would be happy to walk you through this. Here are some of those items. 1) The output of the existing oil fired boiler, BTU/Hr; 2) Either the gpm of the pump or the return and supply temperatures of the water. There is usually an Altitude gauge on the front of the boiler which reads the water temperature and the boiler pressure. 3) It would be helpful to know the return and supply pressures across the pump. 4) Specifications on the stove., etc. There would be more info required, but this gives you the idea. Email me at gerscott@txcyber.com, and we can go from there.

Original windows amount to open wall space other than air exchange from inside to out and vice versa. Add heat reflective film to glass & an inside frame "storm window plastic" as suggested above. A "Heat Wave Fan" <http://www.thermalengines.com/> sitting on the Pellet Stove will circulate the air in the same room (basement?) to assure uniformity of temperature.

"First I thought of cutting into the hot air supply duct work and adding a blower. This would only cool the warm air."

An erroneous assumption. A blower will warm the air slightly not cool it.

Why not go first class and get a knowledgeable HVAC contractor to survey this "Old House" and make comprehensive recommendations based on his survey and expertise.

Based only on your description and not seeing the actual house leaves everyone here at a disadvantage and the possibility of making inapplicable suggestions.

From your description, a simple solution comes to mind.

Break the return ducting to your hot air furnace, so that the cool air from the house enters the basement somewhere near the pellet stove. add a length of duct to the return opening at the furnace to pull air from near the basement ceiling. Bypass the operation of the furnace blower from the furnace heat controls so you can run it "continuously". A variable speed blower would be best, and its easy to replace your existing blower if it is fixed speed. Run the blower at low speed continuously, and when the thermostat in the house calls for more heat, the furnace will fire and turn up the blower. This will maintain the higher blower speed as long as the thermostat is calling for heat, and the furnace burner will cycle on and off as necessary to maintain plenum temperature. Once the thermostat is satisfied, the furnace will turn off and the blower will return to low speed. Done.

A general note on overall furnace efficiency (as opposed to just combustion efficiency) is that the plenum temperature control should be set as low as possible to maintain the desired indoor temperature during the coldest outside temperatures encountered. The lower you can set it, the more efficient your furnace will be overall.

You could get more elaborate depending on if you wanted to maintain a direct return duct for the house to the furnace at times when the pellet stove may not be in use. Additionally, you could pass the return ducting over the stove, with a hood opening into the bottom of the duct and another opening before the hood (upstream in the return air flow) to replenish basement air with the return air from the house, that once heated by the stove enters the hood.

In other words, you are simply including the heated basement in total air circulation flow, thereby circulating heat from the stove.

This is the general scenario I would pursue. I don't see that you should have to knock yourself out with cutting openings in walls and floors, adding blowers etc, when you already have a system in place that circulates air throughout the house, with its own blower and ducting.

I like Greg Cs idea.

Me too, There are alot of problems with putting the two systems together. It is easier to just run the pellet stove in the basement and cut a large opening in the return air duct and let the existing furnace take as much heat as it will. The high low limits someone mentioned before would have to be adjusted, but not a big deal at all. Let the pellet stove rip, make the adjustment to the existing furnace so a hotter retun air will still allow it to run. The cellar gets heat and the resistence of the first floor is poor, so transfer of heat through the floor works well without cutting any openings in the floor that would trigger having to install fire dampers. It's trial and error at that point, but will cut way down on running the existing oil burner for sure. Note: Combining flues could be a problem with the local Fire Chief or Fire Prevention Officer. They would hate to see a Carbon Monoxide situation. The codes regarding flues and venting have changed here in Massachusetts. New Hampshire is pretty strict too.

The idea is good and logical........BUT, let me add a word or two of caution. Using a room as a return air plenum, invites more dirt and dust, etc into the air system. I would suggest you install a good quality filter on the return air opening of the oil fired furnace with a "throw away" filter ahead of the 'good filter', for frequent and inexpensive changing.......... AND, keep chairs, tables, cloths, toys, etc away from the furnace return air opening. Don't use the area as a storage area! I have found this to be the case so many times in the past, in office buildings, schools, etc. where the owner insisted on using the heating/cooling equipment room as a storage room......You get the picture........

OLD F**T:

I agree fully .... I'm never sure how much verbiage is enough or too much.

I was assuming the case where the return filter was at the furnace itself, and did mention ducting it up to receive air from near the ceiling of the basement. Extra filtration is always a good idea, and especially in the case where some surfaces of the pellet stove is likely at a high enough temperature to "sinter" airborne dust which then becomes an irritant or at least makes breathing the air feel dryer than it is.

I too have seen so many cases of things partially blocking return openings. In older houses, which often had a single large return register for the whole house, cold rooms could occur from no return path as would be caused by the door bottom gap being taken up by carpeting.

I also commonly saw that heating service personnel would tend to set boiler or plenum temperatures much higher than desirable from an efficiency standpoint, just to minimize the chance of a service call about insufficient heat on the coldest days.

Forced air heating has the potential to be the most comfortable and most efficient if installed optimally (and it is the only type of heating where you can treat all the air in terms of filtration and humidification) ... but it so rarely is by builders or contractors whose primary goal is to minimize installation cost.

Regards,

Greg

I agree. In the return opening it would be easy to add the fliter rack and some wire mesh screen across the opening. There are alot of details for sure that should be thought about due to the nature of the beast.

Any feedback on what finally worked? I am putting a pellet stove in my fininshed basement. I have forced hot air with the intake to heater in finished area. I was simply going to tiurn off heat abd run jsut the fan when I have the pellet stove running which should circulate the heated air in basement throughout house thorough vents. Am I oversimplifying something?