Why I suggest, if designing your own home, put the furnace/AC unit inside the living area.

[INresponse]

I designed and built my own home. I set up the floor plan on my computer and brought it to an architect to tweak it and make up the prints to submit for the building permits. One thing I didn't know about back then was where to put the HVAC unit. My previous home in Las Vegas had it in the attic, my parents home growing up in Michigan had it in the basement. I didn't plan any space inside the living area for the HVAC unit and assumed the attic was the proper place in new construction, and the architect didn't discuss it with me so I didn't know any better. When I contracted with the HVAC company for the install the plans had it in the attic so there was no discussion from them either, and attic install is the norm for this part of the country.

What have I learned since then? In the summer all the duct work and the HVAC unit in the attic get very hot, about 120* or so in the heat of the day, and when the unit cycles on it spends the first couple minutes blowing hot air into the house until the duct work cools off. The flexible ducts are insulated, maybe an inch of cheap fiber, but between cycles they get hot. So, for the first few minutes the AC is warming the house before it starts to cool the house, wasting money. Now that it is cooling down for the fall, maybe in the 60's during the day and about 40 at night the HVAC unit and the ducts are cooling off in the attic and they are pumping cold air into the house before they warm up to heat the house, wasting more money. BUT, late last night before the heat started kicking on for the night I walked around with an infrared thermometer to check the walls and ceilings to see how the walls and ceilings were holding the heat in the house and everything was about the same temperature as the inside air, right about 63* but when I aimed the thermometer at the HVAC vents in the ceilings they were all reading 52* because they are cold in the attic and the cold air was dropping from the vents into the living areas. On top of that when sitting or standing below the vents there is a cold draft dropping from the vents into the living areas cooling off the house and wasting money.

Based on this experience, if I knew then what I know now I would have placed the HVAC unit in the back of the big walk in closet off the main hallway so that it would maintain a more reasonable temperature all year long. The duct work would have been inside the interior walls or inside the insulated floor trusses between the first and second floors. Yes, the HVAC room would have need a vent to allow in outside air, and of course the chimney would still be venting out the roof, but for the most part that HVAC room would be closer to the temperature of the living areas and would not be 120* in the summer or 30* in the winter.

Just what I learned and something that I will definitely do when building any houses in the future, and thought I would share this for anyone planning to design and build their own home in the future. Most of us want our homes to be very efficient, and now I know the placement of the unit in the attic is NOT efficient and is wasting money.

 

[SheepDog]

When heating your house the heat pump gives off cold air. When cooling your house it puts out warm air. There is no good reason to have that going on inside the conditioned space. Use a multi-split system so the only fluids in the house are the ones in use. The exhaust stays outdoors and the indoors stays at the temperature that you want. Use a geo-grid to pre-treat the air so it stays close to 55F and that will lower your heating and cooling cost all year long. A geo-grid well can also be used for the working fluids. Getting rid of the heat in summer and getting rid of the cold in the winter. It all makes the air system more efficient.

 

[INresponse]

When heating your house the heat pump gives off cold air. When cooling your house it puts out warm air. There is no good reason to have that going on inside the conditioned space. Use a multi-split system so the only fluids in the house are the ones in use. The exhaust stays outdoors and the indoors stays at the temperature that you want. Use a geo-grid to pre-treat the air so it stays close to 55F and that will lower your heating and cooling cost all year long. A geo-grid well can also be used for the working fluids. Getting rid of the heat in summer and getting rid of the cold in the winter. It all makes the air system more efficient.

In many areas of the country the HVAC unit is inside the living space of the structure, across the midwest from what I am familiar with if a home has a basement it is in the basement not in the attic. I think you are referring to the AC compressor, you specifically mentioned the Heat Pump unit, both of which are required to be placed outside of the structure completely. I am not suggesting the compressor be inside the home, I am suggesting the furnace/AC coil/blower be inside the the living area. AC compressor/condensers and Heat Pump units are always placed outside, that is a given.
The point I am making is duct work and the air handling unit (blower) in the attic warms up in the summer and cools off in the winter. The duct work has minimal insulation so in the attic space in the summer when the sun beats on the roof the attic gets real hot. In the summer when it is 100* outside and the sun beats on the roof and heats up the attic to at least 120* that duct work, and the HVAC unit in the attic get HOT. The compressor kicks on first and after a minute the blower starts circulating the air BUT the ducts are hot and take a few minutes to cool off. The opposite happens in the winter, cold instead of hot. Regardless of the system the ductwork will get hot in the summer or cold in the winter. Someone could have the most efficient system, 20 or 30 or 50 or 1000 SEER, but the ductwork will still acclimate to the attic temperature, hence the problem I described in the original post.

 

[Terri9630]

We just put in a mini split. No ducting.

 

[INresponse]

We just put in a mini split. No ducting.

Sounds like a good option. When I was pricing the split system was well over twice the price. (edit: both HVAC units and the duct work would have still been in the attic unless I had a separate unit for each room which would have cost almost as much as the materials to build the house) My system would have been fine if I knew enough to place the HVAC unit inside the living area of the home instead of in the attic. I just thought it would be helpful information to others who might be planning to build a new home.

 

[Neb]

Sounds like a good option. When I was pricing the split system was well over twice the price. (edit: both HVAC units and the duct work would have still been in the attic unless I had a separate unit for each room which would have cost almost as much as the materials to build the house) My system would have been fine if I knew enough to place the HVAC unit inside the living area of the home instead of in the attic. I just thought it would be helpful information to others who might be planning to build a new home.

I run the blower constantly. Would that help you?

Ben

 

[Aerindel]

In many areas of the country the HVAC unit is inside the living space of the structure, across the midwest from what I am familiar with if a home has a basement it is in the basement not in the attic.

Yep. I've never seen one anywhere else.

 

[Cabin Fever]

Our HVAC is in the basement of our home.

 

[INresponse]

I run the blower constantly. Would that help you?

Ben

It would, but it would definitely bump up the electric bill.

My situation is not dire, we are not freezing. In another month or so when we start using the wood stove in the living room the heat from the stove will rise up into the ductwork and keep them warm so I am not concerned about the minor problem. The worst of it is just the extra cooling costs in the summer because it does blow hot air into the house before it starts to cool the house, which isn't seriously bad but it is adding a bit to cooling costs.

I just wanted to share the information for anyone else considering building a new home. It is something to think about when designing a new home. It would be simple enough to plan a small bit of space within the climate controlled envelope of the home for the HVAC unit. Had I know ahead of time I would have placed it in the back of the big walk in closet off the main hallway and made a simple access panel to separate it from the closet. For most people it isn't a problem but if someone was making a serious effort to build a new efficient home with the hopes of saving on energy costs I think this would be a very helpful step in making the home more energy efficient. For most people ..... they really wouldn't give half a damn.

 

[Supervisor42]

It would, but it would definitely bump up the electric bill.

My situation is not dire, we are not freezing. In another month or so when we start using the wood stove in the living room the heat from the stove will rise up into the ductwork and keep them warm so I am not concerned about the minor problem. The worst of it is just the extra cooling costs in the summer because it does blow hot air into the house before it starts to cool the house, which isn't seriously bad but it is adding a bit to cooling costs.

I just wanted to share the information for anyone else considering building a new home. It is something to think about when designing a new home. It would be simple enough to plan a small bit of space within the climate controlled envelope of the home for the HVAC unit. Had I know ahead of time I would have placed it in the back of the big walk in closet off the main hallway and made a simple access panel to separate it from the closet. For most people it isn't a problem but if someone was making a serious effort to build a new efficient home with the hopes of saving on energy costs I think this would be a very helpful step in making the home more energy efficient. For most people ..... they really wouldn't give half a damn.

Another option to consider: our house in Alabama had something called a "package unit" (similar to mobile homes but much bigger).
All ductwork was in the crawlspace under the house and not in the attic, (which got up to 140°F in the summer).
The outlets were all floor vents.
It worked good in the winter too because the crawlspace was sealed off from the outside air like the interior of the house, and not ventilated like the attic.
Any houses that are not built on a slab, with no crawlspace (like us down here ) should have their HVAC ductwork under the floor.

(not our crawlspace)

 

[joel]

 

[INresponse]

Another option to consider: our house in Alabama had something called a "package unit" (similar to mobile homes but much bigger).
All ductwork was in the crawlspace under the house and not in the attic, (which got up to 140°F in the summer).
The outlets were all floor vents.
It worked good in the winter too because the crawlspace was sealed off from the outside air like the interior of the house, and not ventilated like the attic.
Any houses that are not built on a slab, with no crawlspace (like us down here ) should have their HVAC ductwork under the floor.

(not our crawlspace)

In that type of situation, especially sealed off from outside air, that would be ideal.

 

[INresponse]

If I was aware of Rocket Mass Heaters I would have designed the house with a place for one. Now that I am familiar with them I can't find a place it would fit.
I might eventually look at building a RMH in the garage but ....... I need to be darn sure it will be a place that wont be in the way. So far I haven't figured that out yet.

 

[Supervisor42]

If I was aware of Rocket Mass Heaters I would have designed the house with a place for one. Now that I am familiar with them I can't find a place it would fit.
I might eventually look at building a RMH in the garage but ....... I need to be darn sure it will be a place that wont be in the way. So far I haven't figured that out yet.

I just don't know how they deal with the creosote buildup in the big u-shaped pipe under the seats. Whenever you cool the exhaust from a wood fire, creosote forms.
Cleaning a straight vertical chimney pipe is easy.
If built-up creosote lights off, you have flames and sparks belching out of the chimney.
(Don't ask me how I know )

 

[Bacpacker]

Our unit and most ducting is in the basement

 

[viking]

Somewhere on this site I talked about seeing an earth bermed home I visited just south of Grants Pass, the owner had built a huge floor to ceiling Russian stove out of stone, probably 4' wide by 8' long, there were baffles inside to direct the hot smoke in a zig-zag pattern throughout the stove, heating the stones, all that was needed was an initial large hot fire and the stove would give off heat all night.

 

[HippoTwilight]

First design to Passive House standards to minimize your energy demand for thermal management (burning wood counts as energy). Then look into Net Zero, which uses on-site energy generation (renewables) to handle the remaining electric load. If you're environmentally conscious, there's multiple levels of LEED certification too.

We have 2 floor plans picked out for our next home. As I type this, I have every intention of building to Passive House standards. HVAC is planned to be an ERV, some kind of multi-zone heat-pump system, and a dehumidifier. I haven't decided on ground or air source, but I'm leaning toward air b/c the newer inverter units are so much better now, and the construction cost of ground source is astronomical. All the equipment will be housed in a full basement that is included in the conditioned envelope of the house.

 

[INresponse]

Our unit and most ducting is in the basement

That is exactly what I am suggesting. I know usually the basement is cooler than the upper levels but that will be a bonus in the summer for AC use and a very minor difference in the winter compared to placement in an attic. Placing the HVAC within the envelope of the living area of the structure will help it to maintain a more stable temperature. The temperature extremes in an attic are hindering the efficiency of the unit.

 

[viking]

uWe have a large open area behind a concrete wall that I have been considering burying a culvert to pull cool air from for cooling our home, as it is now, during hot summer days, we open a lot of windows just after sunset, turn on a few fans and dump the warm air in the house during the night, at just around 9:00 AM, the fans are shut off and windows closed, these actions generally keep our home up to 20 degrees cooler during the sunlight hours. We also have a large Big Leaf Maple to our west and a tall Black Walnut to our south that really help in cooling. Another thing that seems to make a difference is when I installed a rib lock metal roof I had built the sub roof with two foot overhangs which helps to shade the outside walls, it also which is just a double sheathed roof with two vent systems, I couldn't afford to do the south side of the roof but the attic is well insulated. The small wood stove has been more than adequate to heat our home, our average firewood use per winter is around one cord. It really pays to think things out and in doing so we have kept our electrical bills way below normal. The only regret I have in not following through with one of my ideas is running a main hot water feed under the floor to the wood stove so that I could add wood heated water with water coils mounted on the sides of the stove.

 

[INresponse]

uWe have a large open area behind a concrete wall that I have been considering burying a culvert to pull cool air from for cooling our home, as it is now, during hot summer days, we open a lot of windows just after sunset, turn on a few fans and dump the warm air in the house during the night, at just around 9:00 AM, the fans are shut off and windows closed, these actions generally keep our home up to 20 degrees cooler during the sunlight hours. We also have a large Big Leaf Maple to our west and a tall Black Walnut to our south that really help in cooling. Another thing that seems to make a difference is when I installed a rib lock metal roof I had built the sub roof with two foot overhangs which helps to shade the outside walls, it also which is just a double sheathed roof with two vent systems, I couldn't afford to do the south side of the roof but the attic is well insulated. The small wood stove has been more than adequate to heat our home, our average firewood use per winter is around one cord. It really pays to think things out and in doing so we have kept our electrical bills way below normal. The only regret I have in not following through with one of my ideas is running a main hot water feed under the floor to the wood stove so that I could add wood heated water with water coils mounted on the sides of the stove.

Reading this, had I know of this when designing the house I would have made this happen. Maybe two water lines, the first being to warm the supply water a little as it comes in the house. About this time of year the community water tanks start cooling down so the water coming in is getting cooler. Cooler water isn't a bad thing, I think it hovers about 55* during the winter months, but the damn new fangled water heaters don't heat the water as high as they used to so "safe" temperature hot water cools off fast when you dial in the cold water to the shower. I like plenty of water pressure in the shower and the new, low flow, water faucets don't give enough pressure unless you open both hot and cold faucets. I have talked about placing a 100 gallon or so water tank inside the house so the supply water will have a chance to warm a bit before it flows to the rest of the house. I may be over thinking this and should probably just settle for what I have but unfortunately my pea sized brain is always thinking about how to make things better.

 

[The Lazy L]

...Any houses that are not built on a slab, with no crawlspace (like us down here ) should have their HVAC ductwork under the floor.

Since warm air rises and cold air falls, hot air registers should be in the floor and cold air registers in the ceiling.

 

[SheepDog]

What about the air return? You would need to switch the air flow winter to summer each year.

 

[Neb]

What about the air return? You would need to switch the air flow winter to summer each year.

I do.

Ben

 

[INresponse]

Cold air shouldn't fall on the bed, sofa, desk and other places where people stay for a long time. The maximum concentration of cold air is observed at a distance of 2-3 meters from the air conditioner, then the coolness dissipates airconservicingsingapore.com. The optimal space between the ceiling and the upper border of the indoor unit of the split system is 10-15 cm. Warm air is taken from the apartment through the upper part. That is why it is so important to leave enough space for the free circulation of air masses.

I know that makes perfect sense, to someone, but it confused the heck out of me.

Are you referring to when the A/C unit is running to cool the home during summer months? If so than I understand. If not, you lost me.

 

[Frodo]

we have here in my area a room called the HVAC closet
it is in the garage elevated 24'' off the floor the space under the unit is the return air plenium with a grill on the wall inside the home
the closet is 5' wide it houses the hvac unit and the water heater
A piece of 4'' pvc is installed under the slab and comes up into the closet. the freon set lines are pulled from the unit outside into the closet via this pipe

 

[Aklogcabin]

Burying your fresh air intake in the ground you can take advantage of the near constant soil temperature to cool or preheat any fresh air used either for fresh air to home or to make up air for your furnace.
Also nice to put your hot water heater as close to the bathroom or kitchen as possible so when you turn the hot water on your not waiting so long. We will be using a toyo boiler with an on demand hot water unit. I will run the hot water lines right next to the in floor heater tubes so it warms it. Should come out of the faucet fairly warm at start.

 

[Frodo]

run a circulating line on the hot water, to save energy control the circ pump using the light switch
when you walk in the room and turn on the light the pump starts and you have hot water by the time you turn on the faucet, turn out the light, pump stops, and you save power .

 

[SheepDog]

Frodo,
I've been thinking of using a hybrid water heater to work with the re-circulating hot water system. A regular water heater initially heats the water and the re-circulating water is kept hot with a heat pump. The entire hot water loop is kept at temperature so there is no lag time at all. It does require a lot of insulation on both the hot and cold water lines. The plastic lines are better at retaining their heat but still need the insulation to work well.

 

[Frodo]

here is all you need to circ the water

 

[Frodo]

what a lot of people do not understand about a circ line is the way the piping needs to be installed

if you want the whole house hot to be circulated then you can not have dead ends.

water will follow the path of least resistance and if their is a dead end the circ water will not enter it