I'll soon be working on converting a second floor of a residential building that was never finished and is being used as an attic for the last 80+ years. Building Size 36'x36', 9 1/2' 1st floor ceiling height, 8' planned ceiling height in 2nd floor with plenty of insulation and air barrier planned. This is also a DayCare Facility.
I will be adding an open stairway to the floor plan to provide access to the 2nd floor. (Clients request for capitalizing on the natural daylighting.)
The HVAC guy informed me that: having 2 separate HVAC systems is the route he would use because-it was how he learned and is the norm in St Louis:
The RED warning light that is going off in my head and is contrary to all I've learned is that: "What will keep one system from robbing the climatized air from the other system?" The open stairway will allow air movement up and down.
I agree with him partially on 2 systems if there was not an open stairway planned.
Since this is in design stages to capture the natural lighting I've mentioned a French door with a wall would allow lighting and separate the floors. Which makes a dual system more appealing to me.
Thanks in advance for any advice.
The following CAD drawings were made using Sketchup and what I've found is an easy way to convert plans into picture files for showing my clients what the finished product will look like. Yes there will be rails on the stairs, omitted so that it doesn't clutter up the drawing.
Instead of this railing set up a wall with a French door would allow the natural light into the room. And also alleviate my fears of a child climbing the rails and falling to the 1st floor. If this design is chosen I plan to build the railing 48" tall.
Bob and Curt, sorry my posts left the cascade I know it makes following the conversational thread frustrating and confusing - ipad does not want to reply in line.
Bob: " We have to get down into the 30's before the heat runs much."
What does that mean? Seriously, you aren't suggesting that there is no load on residential structures at 40f, are you?
If you look at consumption I think you'll find that most of it occurs above 30 for most of the country. So maybe stepping back and asking: "WHY DO We have to get down into the 30's before the heat runs much" would open up another area to consider.
If cycling on and off, overheating air, duct, and house and shutting off are inefficient, what is happening at 30 and above if your equipment "doesn't run much"?
Furthermore is it comfortable to heat that way? I think it is not, and so people bump thermostats, use space heaters, overheat parts of their homes (even opening window) in an attempt to get other parts comfortable. Stupid Pet Tricks - we've done them and seen them.
So I go back to the idea that having lots of stages is good for efficiency and comfort. I've sold LOTS of hybrids and I FOLLOW UP. Reports from happy clients about amazing comfort and amazing energy savings.
Curt, have you run the number on SEER savings from HP to straight AC? I need to factor that into my designs so people understand there is a small sacrifice in efficiency, and how that might translate to $.
Not saying we don't need any heat in the 40's, but heat loss is relatively low. Once the furnace has recovered from night setback (we setback for comfort reasons more than saving energy) it's done for the day. We've only started hitting the high 30's for morning lows in Oklahoma, it will be interesting to see what happens once winter gets here.
I'm with you on the "stupid pet tricks". People turn their heat to 72-75 in the morning then run the AC in the afternoon of the same day.
I have concerns about ductwork losses when running low BTU outputs. Our ductwork is in the attic and is of decent tightness (not perfect, but better than most). Does running low delta T cause more "loss"? If ductwork looses 5 degrees due to running through unconditioned space wouldn't that hurt the 90F discharge temps more than a 110F discharge temp of the air handler?
I have not; all my residential clients get HP since we have enough of a heating season to justify the expense.
I think you could safely figure the efficiency hit at 5-10%
Sounds about right. In SoFla, heat might be needed just 10-20 days per year with an energy cost of $50-100
In NoFla, heat is needed intermittently in November and March, consistently Dec-Feb.
It looks good. Your HVAC guy is right on this. It's good to use two systems for the two floors. 1.5 ton should be perfect for the downstairs unless there are some heavy internal loads. Your AC work the most for your upstairs work. If you have any issues or need to talk to the residential HVAC services experts then you could contact at White Mechanical, Inc. to get more suggestions on this.
And I would have a system check on the 1st floor 1.5 ton unit to make sure it is performing up to spec. Then look to see if the system was sized right. If its a day care you might have a higher temp load on the system during the day and would need to be sized to this. Over sizing an A/C unit will cause issues as well and not allow the system to draw out humidity. I would look to add a dehumidification unit to the 1.5 ton central a/c unit. It might be putting out enough btu's of cooling to satisfy the load but not drawing out the humidity. This would cause a comfort issue.
It seems the question was asked in Nov of 2013 maybe the OP will reply and tell us how the system has worked for the last 4.5 years.