How to duct room on cement slab?


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Old 06-09-14, 09:19 AM
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How to duct room on cement slab?

I bought a ranch style house and the previous owners put a 12'x20' addition on the back on a cement slab. You walk into the room from the east wall off the kitchen. There is about a 10" drop from kitchen to slab addition. They used a 2x8 as a rim joist on house. In the 2x8 joist in the doorway from kitchen to slab is one 2x12 duct this is the only airway. The west side of the room has a wood stove. I want to build a 2x8 floor on the cement slab to make it the same height as kitchen and run duct work and tee it off so the room with be heated and cooled. if i just bought more 2x12 duct and tee it off would there be enough airflow or how should i do it?
 
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Old 06-09-14, 09:36 AM
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Welcome to the forums.

Are you planning any cold air returns in the room?

Not my area of expertise but I would think two vents on the periphery of the room and at least one return close to the kitchen would work pretty well.
 
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Old 06-09-14, 10:09 AM
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I never though of cold air returns. The room has cathedral ceilings by the way.
 
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Old 06-10-14, 04:39 AM
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Just put in a ductless split. It will heat and cool that room easy
 
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Old 06-10-14, 05:12 AM
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mallard -

With the vaulted ceiling it sound like the room will normally be connected to activities in the rest of the house. If that is the case, make sure the existing HVAC supply can handle the extra seasonal loads.

If it has the capacity, the raised floor will eliminate the cold winter floors and allow a return for more whole-house comfort. Much depends on you climate since there are some substantial differences between the southern "flatlands" and the northern areas or near the big water (lakes Huron, Michigan and Superior).

I would make sure there is a return back to the HVAC unit and then get a good ceiling fan (remote with no chains) for circulation and uniformity.

I now have a two level home (in a colder climate, humid summers with an open staircase and uniformity of temperatures is necessary for comfort. - I run my furnace fan 24/7 in the winter for circulation. In the summer air conditioning is a necessity, so when it is "closed up" in the real summer I use the system at a constant temperature because it more economical (plenty of concrete and thermal mass) and use a fan setting on the "auto" setting for maximum humidity. In the transitional seasons, I wing it and try to avoid fights with my wife. I have a newer 80% efficiency furnace with an ECM fan. and an older AC unit, but my ceiling fan in the vaulted living room, dining and part has not been turned off for 6 years.

That seems to work for me.

Maybe some of this could be of help for your situation.

Dick
 
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Old 06-10-14, 07:38 AM
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This room is our living room so a lot of time is spent in it. The house is small 1200sqft including the addition. How do I find out if my furnace is capable of this? I just assumed it would be due to the small size of the house. In the summer months the room is fine but in the winter it is pretty cold. I will look into the ductless split I was also planning on taking the wood stove out and putting a gas fireplace in. I'm not sure if i want to rely on a fireplace to keep the room warm when were not home.
 

Last edited by mallard1123; 06-10-14 at 08:05 AM.
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Old 06-10-14, 08:48 AM
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Gas direct vents are very good and efficient if you have decently located stack. Very pricey, but nice with all the goodies "multi-speed" fans, thermostats doors and trims. I was going to replace a wood burning fireplace with a direct vent insert to use the chimney. I did not do it until we found out that our 2 year old 80% could handle the home because of the number of vents and especially the number of returns that could be tuned(opened ot closed) one or twice a year. We sealed/closed off the chimney and covered the opening when we decorated.

My situation may be unique with a north facing lower level with a north exposure and an oversize slider and a 4'x6' slider window. In the, winter the upper level vents are shut down a lot and the lower level opened completely with enough lower returns to collect the cool air that flows down the open stairway. Every home is different and you have to play around and find out the changes over a few days.

Dick
 
 

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