2 system house question

[sleek98]

There has been a lot of information in this tread. Most of it seems to be accurate, but accuracy often need to be tempered with a little common sense.

Many people site smell as the reason for not having return air ducts in bathrooms and kitchens. Just about all bathrooms and kitchens have supply ducts. If you push air into a room, an equal amount of air has to leave the room. In typical bathroom, air can exit either through a bathroom vent (which is normally run for only short periods of time) or through an open door. Most kitchens don't seem to have doors these days, and only a small percentage seem to have vents to the outside. Even though these rooms don't have return air ducts, the air and the smells are being returned in some fashion.

Supply ducts are often placed above or below windows in an effort to maintain an even temperature in a room. However, some houses (like mine) are designed (by the location of light switches, electric outlets, cable outlets, etc.) so that the only logical place for a bed in a bedroom is directly in the path of a draft from the supply duct. A different type diffuser could direct the supply air in a different direction, but it doesn't make much sense to run a longer duct to an outside wall, then install a diffuser that directs the airflow to the other side of the room.

Having separate return ducts for each room makes the most sense in situations where the rooms are "sealed" off (most often by doors). Transom grills can be effective air returns, but are more prone to transmitting light and/or noise between adjoining areas. This may be more of a problem with bedrooms.

In my humble opinion, having a separate system entirely located on the second floor would give you the "best" HVAC. However, I doubt that your floorplan was designed so that HVAC was given the highest priority.

As a side note, now would be a great time for you to think about where you may want to install curtain rods, towel rods, etc. and install some wood blocking behind where they will be mounted.

Knowing now I would have pulled out the master bedroom the extra 3 foot to match the main floor and put it up stairs in my closet.

Good idea on the curtain rods. I was planning on doing it but completely forgot.

 

[eddieK]

There has been a lot of information in this tread. Most of it seems to be accurate, but accuracy often need to be tempered with a little common sense.

Many people site smell as the reason for not having return air ducts in bathrooms and kitchens. Just about all bathrooms and kitchens have supply ducts. If you push air into a room, an equal amount of air has to leave the room. In typical bathroom, air can exit either through a bathroom vent (which is normally run for only short periods of time) or through an open door. Most kitchens don't seem to have doors these days, and only a small percentage seem to have vents to the outside. Even though these rooms don't have return air ducts, the air and the smells are being returned in some fashion.

Supply ducts are often placed above or below windows in an effort to maintain an even temperature in a room. However, some houses (like mine) are designed (by the location of light switches, electric outlets, cable outlets, etc.) so that the only logical place for a bed in a bedroom is directly in the path of a draft from the supply duct. A different type diffuser could direct the supply air in a different direction, but it doesn't make much sense to run a longer duct to an outside wall, then install a diffuser that directs the airflow to the other side of the room.

Having separate return ducts for each room makes the most sense in situations where the rooms are "sealed" off (most often by doors). Transom grills can be effective air returns, but are more prone to transmitting light and/or noise between adjoining areas. This may be more of a problem with bedrooms.

In my humble opinion, having a separate system entirely located on the second floor would give you the "best" HVAC. However, I doubt that your floorplan was designed so that HVAC was given the highest priority.

As a side note, now would be a great time for you to think about where you may want to install curtain rods, towel rods, etc. and install some wood blocking behind where they will be mounted.

Supply air outlets are located at outside walls to make sure to attack the infiltration, be that heat gain or heat loss.

This is considered a perimeter type system. This way you can condition with the least amount of air noise, bar type supply registers allow you to deflect the air at an angle into the room and deflect to both sides, or just one. This way the "throw" can be altered away from items you don't want air flow on.

That air is on it's way through the room, on the way to the return where it can be reconditioned and sent back through the system. Doors should be undercut, this prevents doors from being affected by negative or positive pressure differences that would normally not be noticed.

If you need to provide pass through air by a wall (the "transoms" some keep referring to - never heard this term used for these before)...you simply cut a small grille into the wall low on one side and hi on the other...this way light is not deflected.

 

[sleek98]

Transom must be a midwest thing. I have never heard them called anything else.

 

[tomroblee]

I think that the term "transom" is based on small transom windows that were placed above doors or above larger windows for ventilation years ago.

Air will pass through any opening if there is a pressure differential between the two sides. Undercutting doors may not be aesthetically pleasing. Hallways often function for return air. Placing one vent high on the wall and one lower will avoid having light pass through, but doing so can be problematic if the only wall area between a bedroom and a hallway is a small rectangle area above a door.

I'm a geezer and have spent time in many older homes that originally had coal fired gravity heating systems. The original coal furnaces were located in the center of the basement, and the ductwork system was composed of large ducts that ended at inside wall of most of the rooms. (Without a blower, it just wasn't practical to extend the ducts to the outside walls.) When these homes were later converted to "modern" forced air, the original ductwork (to at least the second floor) was generally left intact. By modern standards, the ductwork systems of these homes would be criticized by many. However, the people living in these homes are quite comfortable.

 

[sleek98]

Got the two systems installed.

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