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Ductless, Mini-Split Heat Pumps
Ductless, mini-split-system heat pumps (mini splits) make good retrofit add-ons to houses with "non-ducted" heating systems, such as hydronic (hot water heat), radiant panels, and space heaters (wood, kerosene, propane). They can also be a good choice for room additions, where extending or installing distribution ductwork is not feasible.
Like standard air-source heat pumps, mini splits have two main components: an outdoor compressor/condenser, and an indoor air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing, and a condensate drain, links the outdoor and indoor units.
Advantages
The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. Many models can have as many as four indoor air handling units (for four zones or rooms) connected to one outdoor unit. The number depends on how much heating or cooling is required for the building or each zone (which in turn is affected by how well the building is insulated). Since each of the zones will have its own thermostat, you only need to condition that place when someone is there. This will save energy and money.
Ductless mini-split systems are also often easier to install than other types of space conditioning systems. For example, the hook-up between the outdoor and indoor units generally requires only a three-inch hole through a wall for the conduit. Also, most manufacturers of this type of system can provide a variety of lengths of connecting conduits. If necessary, you can locate the outdoor unit as far away as 50 feet from the indoor evaporator. This makes it possible to cool rooms on the front side of a building house with the compressor in a more advantageous or inconspicuous place on the outside of the building.
Since mini splits have no ducts, they avoid the energy losses associated with ductwork of central forced air systems. Duct losses can account for more than 30% of energy consumption for space conditioning, especially if the ducts are in an unconditioned space such as an attic.
In comparison to other add-on systems, mini splits offer more flexibility in interior design options. The indoor air handlers can be suspended from a ceiling, mounted flush into a drop ceiling, or hung on a wall. Floor-standing models are also available. Most indoor units have profiles of about seven inches deep and usually come with sleek, high tech-looking jackets. Many also offer a remote control to make it easier to turn the system on and off when it's positioned high on a wall or suspended from a ceiling.
Split-systems can also help to keep your home safer since there is only a small hole in the wall. Through-the-wall and window mounted room air-conditioners can provide an easy entrance for intruders.
Disadvantages
The primary disadvantage of mini splits is their cost. Such systems cost about $1,500–$2,000 per ton (12,000 Btu per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost twice as much as window units of similar capacity.
The installer must also correctly size each indoor unit and judge the best location for its installation. Oversized or incorrectly located air-handlers often result in short-cycling, which wastes energy and does not provide proper temperature or humidity control. Too large a system is also more expensive to buy and operate.
Some people may not like the appearance of the indoor part of the system. While less obtrusive than a window room air conditioner, they seldom have the built-in look of a central system. There must also be a place to drain condensate water near the outdoor unit.
Qualified installers and service people for mini splits may not be easy to find. In addition, most conventional heating and cooling contractors have large investments in tools and training for sheet metal duct systems. They need to use (and charge for) these to earn a return on their investment, so they may not recommend ductless systems except where a ducted system would be difficult for them to install.
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Combustion Air Intake Installation
This chapter from the Energy Saving Edition book gives a detailed description of the Combustion Air Intake installation, which according to code must be an important element of your HVAC ductwork system. In the chapter you can find pictures of all necessary tools, materials and pictures of the Combustion Air Intake installation. There are 31 pictures. Installation is divided into six steps, which represent the entire project in the making.
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Combustion Air Intake Installation in Pictures
 For years, I was preaching about high necessity of the combustion air intake, but did not have one installed in my own house. I have both - high efficiency furnace and a water heater and a water heater was working just fine, recently I've discovered why! My builder left narrow, but long gap in the overhangs under the bay window and fireplace shaft, and this was my combustion air intake!
Therefore, I've decided to install one, figured out its size, bought materials, took some pictures and posted them on this page.
Also, in order to make this page more informative I included several pictures from another finished basement project. They are just like the pictures taken from my home installation show step-by-step sequence of installation.
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Pictures from "How to Stop Cold Air from Fresh Air (Combustion Air) Vent in Furnace Room" paid page (see below) included.
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How to Stop Cold Air from Fresh Air (Combustion Air) Vent in Furnace Room
Question
My family and I live in MN. Every winter I have dealt with issues of cold air coming from all areas of our 1955 home with a 3-year-old addition with in-floor heat. I finally installed a fresh intake vent that has halted any cold air coming from other areas of the old part of the house.
With all of our gas appliances and vent fans I calculated an 8 inch size vent. The problem is all that cold air is really pouring out of there and I bought a plastic tub that sits right behind the new boiler but the floor in the laundry room is so cold and it spills out into the rest of the basement.
I temporarily placed salt bags for our softener into the opening of the doorway of the utility room to prevent it from coming into the rest of the basement with little success. I didn't think it would get that cold. I even used the R-10 insulated flex tubing for ducting the fresh air, which works great except for the air not staying in the tub.
Before I put this venting in and we had our old boiler, which was 30 some years old, our CO2 alarm went off 2 times in 10 years but I didn't think it was such a big concern with the cold air pouring into the older portion of our house from everywhere. I finally decided to get a new boiler and the fresh air intake.
Is there anything I can do to keep this cold air at bay?
Answer 1
I teach property-rehabbing classes in the St. Paul Community Education Program...so I encounter questions like this all of the time. In my own house, I made my insulated flex duct (fresh air intake) purposely EXTRA long, and formed a very large P-trap out of the flexible tubing (to mimic that of a plumbing P-trap). The thought behind this is that cold air likes to drops (where warm air rises). By forming this very large P-trap with the flexible duct, I am forcing the cold intake air to travel 3 feet UPHILL again before dropping down into an empty 5-gallon bucket.
Also, something else to consider. Once shaping your intake into a large P-Trap like this, if cold air is still pouring in, then you have a large amount of warm air escaping somewhere else in the house (i.e. up a fireplace chimney or similar). Cold air will only pour in like that (after forming the P-Trap) IF warm air is being exhausted rapidly somewhere else in the house.
Hope this helps and good luck!
Answer 2
Our home in Edmonton, AB Canada was built in 2003/2004 and has a near identical setup to yours - two 6" fresh air intakes, one to the cold air return portion and another to a combustion pot that runs to the floor and simply dumps fresh air into the basement. We also have a mid-efficiency furnace (sounds like you do as well) and a natural gas hot water tank with both "chimneys" tied together.
After developing my basement, I've come up with three solutions to our problem:
1) Install a motorized damper designed by Hoyme - Hoyme Manufacturing Inc - Motorized Dampers & Ventilators - North America. This closes the fresh air intake combustion pot and when the furnace comes on it opens up. Depending on who you speak to you may also want it to open up for when your hot water tank runs (I would to be on the safe side to eliminate CO poisoning risks). You can install a heat sensor on the tank that will open the damper up. You can even go as far as installing a second damper for the fresh air intake that goes into the return air ductwork as freezing cold air is not good for your furnace. Downside - cost of the dampers and availability in your area.
2) Relocate your fresh air intake combustion pot near the furnace. Frame and close off the furnace room. Assuming your combustion air requirements are sufficient, install weather proofing/stripping around the furnace room door to contain the cold air within the furnace room.
3) Ditch the mid-efficiency furnace and go with a high-efficiency furnace. This eliminates the need for the 6" fresh air intakes and will require the installation of PVC pipes to the outside of your house for intake/exhaust.
All three of these options are valid in my location but I would suggest consulting with your local authorities and building codes before making your decision.
I haven't decided on what route to take myself. With the basement being finished it's not too cold except I built an office attached to the furnace room so my feet get cold. I've got a blanket tucked underneath the furnace room door to keep the cold air in. For the first couple of years living here I remember very well how cold the basement can get.
I put a lot of thought and research into this so I hope this helps you, good luck!
For years, I've heard about these issues related to the combustion air intakes, but never faced it myself before. However, recently I install one in my house and now I joined a legion of people who trying to resolve this inconvenience once and for all!
At first as many of you, I've searched the web and all the solutions that I found there were just laughable:
1. Drop the pipe down into an empty 5-gallon bucket.
It doesn't work. You can try it at home just as I did - the result is obvious!
2. Forming very large P-trap with the flexible duct, I am forcing the cold intake air to travel 3 feet uphill again before dropping down into an empty 5-gallon bucket.
I even don't want to give it a try, this idea, even if it works is just plain stupid. Just think about it: who in his straight state of mind would buy a box of flex and make a goofy P-trap out of it and after that is all done on top of it, again, drop it in a bucket?
3. Install a motorized damper designed by Hoyme.
Well, this is not a really bad idea, but it doesn't work. It doesn't work because you can hook up this damper to the furnace only, and as it said above: "You can install a heat sensor on the tank that will open the damper up".
Look, the average price for the damper is $225.95, plus shipping and handling. Plus installation, and plus a heat sensor with installation - just too expensive!
4. Relocate your fresh air intake combustion pot near the furnace.
Just read above it doesn't work.
5. Ditch the mid-efficiency furnace and go with a high-efficiency furnace.
This one is just plain stupid, I do not want to even discuss it here!
So, I've looked at all this solutions and come up with my own one. Bought materials, installed it and let it work for awhile. It is working.
Now it is time to share this simple and very inexpensive solution (I spent less than $10 on my 4" combustion air intake) with visitors of my site.
On the paid page, you will see pictures of tools and materials and three pictures of installation with step-by-step explanations.
The price for an instant access to the page is only $1.44.
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How to Use Combustion Air Intake
Homes need to breathe. Fresh air is needed for combustion in furnaces, fireplaces, wood stoves, gas water heaters and clothes dryers. As people make their homes more energy efficient by sealing cracks, adding insulation and doing other things to prevent heat loss, homes can become starved for air. This is especially true when you're using exhaust fans and vented appliances which draw more and more air from inside the house; air from the outside can be pulled into the home, possibly down the furnace vent or fireplace chimney. This is called "back drafting" and can cause carbon monoxide (CO) to form.
CO is a colorless, odorless gas produced when fuel is not burned completely. Automobiles, charcoal or wood fires and improperly vented or air-starved coal, oil and gas furnaces can produce CO.
Be aware of these CO signals:
- Headaches, nausea, dizziness
- Excessive humidity, heavily frosted windows
- Fireplace smokes, won't draw
- Furnace vents back drafts (See Fresh Air Check below)
To prevent homes from becoming starved for air, the Uniform Mechanical Code requires that all new homes be built with a special duct that brings outside air directly to the heating system. All furnace and boiler installations in existing homes are also required to have a combustion air duct.
To determine if your home is receiving sufficient fresh air:
1. Close all doors and windows.
2. If you have a fireplace(s), build a fire. Wait until the flames are burning vigorously.
3. Turn on all exhausting devices, such as:
- Kitchen and bathroom exhaust fans
- Dryers (gas and electric)
- Attic fans
4. Turn on all exhausting devices, such as:
- Heating equipment
- Water heater
5. Turn on all vented gas appliances, such as:
6. Wait 10 minutes for drafts to stabilize.
 7. Hold a lit match below the heating system draft hood air intake (see illustration at right).
o If the match remains lit and the match flame pulls toward the draft hood, this indicates sufficient fresh air. Check draft hoods on all other equipment also (gas space heaters, water heaters and additional heating systems). Return appliances and exhausting devices to their original condition.
o If the match goes out, it means the vent may be plugged and/or the air supply in your home may be inadequate.
o Check for plugged vent connectors and chimneys. Repair stoppage and test again.
o If the match goes out even when vent is clear, additional air must be brought into the structure from outside. Refer to the Uniform Mechanical Code or contact a qualified heating contractor or your local gas utility service department.
If your house is starving for air, a vent or fresh air intake needs to be installed directly to the furnace area; until it is installed, limit use of clothes dryers, fireplaces, furnaces, and mechanical exhaust fans. Operating more than one of these devices at a time can contribute to back drafting if your home doesn't have an adequate fresh air supply.
Materials used for ducting must meet standards described in the Uniform Mechanical Code. Flexible ducting is not recommended because ridges create turbulence which reduces air flow. Before installing a duct, check with your local Building Codes office for size and materials. Here are examples of installations of fresh air ducts.
Duct Supplying Outside Air to Floor in Furnace Area
 1. Be sure duct is sized in accordance with the Uniform Mechanical Code.
2. Place the outside air intake duct (A) at least one foot above grade level.
3. Cover the air intake with ¼” mesh screen and hood.
4. The duct must discharge the fresh air at a level no more than one foot off the floor.
As you understand it’s very important to have a combustion air intake also from the energy saving point of view, especially if you have a mechanical room. The idea behind this is you don’t using conditioned air as a combustion one. Also it’s important to bring a combustion air to the water heater or furnace as close as possible.
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