My first comment is that it is difficult to keep 2-story 3000 square foot house a consistent temperature with one AC system. At this size you would want two systems either in the basement, or one in the basement and one in the attic.

It looks like the contractor wants to run the main duct on the first floor in order to balance the tempatures on the fist and second floors. This is typically is done with houses in my area which have no basements. You end up boxing in the duct work.

If you are gutting the main house, then why can't the main duct work run in the basement and add ducts to feed the first and second floors? The other option is to put an air handler in the attic to service the second floor, and one in the basement for the first floor. This would give the best comfort at a reasonable increase in cost.

I would not make the ceilling height lower than 8 feet.

fur downs for keeping ducts in the conditoned
space is the most efficient way to go.
I did it in my house with 8' ceilings.
but have the layout to make it work without
being too intrusive.

contractor should have shown you the
layout, and explained the size of the completed
fur downs. it may be too late in the game
to go back to the drawing board.

best of luck

Thanks Mike and Energy Rater for your ideas.

Energy rater: My title was probably misleading as the boxes all over main floor are not yet installed, nor are the ducts (except the start of one duct). It is just that the HVAC contractor is planning to install drop down ducts all over main floor. So hopefully it is not too late.

Mike: Thanks for all your ideas. We will definitely explore the option of placing the air handler in the attic and another in the basement. You are quite right that the contractor wants to balance the temperature between the floors. While I see the benefit of this, I can't sacrifice that much ceiling height for this benefit. I will pay more for to avoid these drop down boxes.

We are now planning to get a second opinion and HVAC design from another contractor. Given that the ducts are only for air conditioning and HRV, it seems over kill to us to have to have all these ducts on our main floor. We thought we would be minimizing ducts given all our heat is from in floor.

Below you will find a plan of where all the ducts are proposed for the main floor. The contractor also plans to have more drop down ducts in the upper level as well as basement. The shaded areas represent all the areas that are proposed to have drop down boxes. The size of boxes are marked as some will go lower than others.

Thanks,

Carol

Do you think we should install ductless air conditioning (such as Mr. Slim). I have just read lots of good things about ductless. What would be the disadvantages of going with ductless vs central air? Am I correct to assume intalling a ductless system might be cheaper than installing both the ducts and and central air conditioning system (we don't currently have ducts for heating due to radiant floor heat, also our walls and ceilings are currently all open due to renos/addition).

Carol

The disadvantage of the ductless in your case it that it will be difficult to get an even air temperature distribution throughout the house. I think it could work in dining room, kitchen, and great room area due to the open design. But it may not work well throughout the rest of the house. It is worth investigating as an alternate solution.

Don't disc out the considerable time that the first contractor invested in the design. It is too bad more time was in invested in information exchange with respect to the duct requirements.

Mini splits, ductless or ducted, might help you out. Note that some can be combined with HRV, You might find that some combination of a larger central system will work for parts of the house while you might use mini splits for others. Take a look at the systems available from Mitsubishi, Sanyo, Toshiba and other manufacturers.

Retrofitting houses without ducts is a real strength of ductless AC. You have already torn the place up so I suspect that a ducted system will be less expensive to install than mini splits. What is better for you is a matter that you have to decide. One advantage to ductless is the inherent zoning. One disadvantage is the inherent zoning. That might be confusing so let me give you an example. If you have a big party, the ductless unit has to be sized to handle the size of the crowd in that room. If you have a ducted system air will circulate to the large, main system allowing it to cool the room where you really need it.

Hi Mike and Ionized,

I appreciate your feedback and info on the ductless systems - very helpful to read your pros and cons to this mini split ductless systems.

I definitely will not discount all the effort the HVAC contractor has spent planning out in his head the air conditioning duct work, and know he had our best interests at heart. He is a great guy, and we will definitely find a way to make right with him for his planning efforts and labour on this part of the job. I just wish he had shared with us that he intended to have drop down boxes in our main floor as soon as he thought of the idea, so we could have told him right away that we would prefer to go another route. We did not discover this plan until he started to install a large drop down duct in the middle of our kitchen and great room (this duct will take 11 inches of head room over a very frequently used artery in our house).

While, I agree the system he planned for would be even in terms of temperature differentials, I wonder how many 8 foot ceiling houses (or any house for that matter) have drop down boxing in their main level to the extent he was planning for (see all the shaded areas on our plan for all the proposed boxes). I have never seen boxing in a main level house before (virtually all houses around here have basements where the vents are located with other vents hidden in walls). I worry that these extensive drop down boxes will devalue the house and any future buyers won't even inquire how even the AC temperature is as they will already be turned off the house due to the low head room caused by the boxes.

When I stand under the one drop down duct he has already installed, I feel very uncomfortable and that is before the boxing, drywall and 3/4 inch hard wood is installed. I am 5'8" and my two older sons are close to 6 foot and not finished growing. I have nephews who are 6'5", and I imagine they would not feel comfortable in our home either.

If you have seen boxing to this extent in main level houses around your area can you let me know? Maybe I am over reacting.

Carol

I agree the amount of ceiling be used seems excessive. I used to own a 2-story house built on a slab and the boxing of the main duct was much less. I don't think you are over reacting.

Is the basement finished? If not, I don't understand why the ducts can not be run through the basement and within the walls. I am guessing that it is to be finished off. Where in the diagram is your air handler to be installed with the first design? It is for all three levels?

You are in Ontario? The climate there is pretty cool compared with most areas where cooling might be desired. With mini-split air handlers (not wall-mounted units), you might be able to cut down on long duct runs minimizing the fur downs. One small air handler might be located to serve multiple rooms in a well sealed and insulated house in a less-demanding climate. In fact, 5000-6000 BTU from the smallest wall-hung equipment meant to serve individual rooms might be too much for most of your house. In other, larger rooms, you might choose alternate equipment meant to serve one room.

All of this might make your single, "huge" HRV system more difficult or impossible to implement. Note that I am not an HVAC pro, just a home owner with mini-splits in a hot, humid environment. You might need an installer with an imagination and with some desire to try new things to even approach something that might be considered unconventional in your area.

Hi Ionized,

Thanks for your reply. Sorry to be so slow to respond -- crazy week at work!

Here are some answers:

1) The basement is currently down to studs. So yes, any ducts can go there. Our plan is to finish the basement as well.

2)The air handler was, in the original plan, proposed to be installed in an existing closet that opens to the hall. This closet, on the posted plan, is in the kitchen area right beside where it is marked fridge (although we now will have our fridge closer to dining room table). The air handler has been bought and it measures around 70" X 21" X 21.5", and it is a Carrier Brand (sorry can't read the other specs on it because it is pushed inside a closet at present). It was bought several months ago and has sat in our home unused, but I doubt at this point it could be returned. However, if necessary we might be able to sell this unit and start fresh with two smaller units. I am willing to make any necessary changes and absorb any extra costs to reduce the need for fur downs in the main living space.

The HRV was to be a Life Breath and I think the contractor wanted it to go to all baths, kitchen, laundry anyway. Given the unit has yet to be purchased, we could get a different size than was initially planned on by the contractor.

As per our weather, we are in Southern Ontario, so our weather is similar to say Buffalo, New York. From late May to mid Sept at a minimum AC is required for comfort most days. We don't have very mature trees either.

Thanks for your comments, and any more comments welcome.

Carol

Carol,

Something here seems fishy. Why would the contractor buy an air handler months before it is to be installed? Will the installation be done by an HVAC sub-contractor?

I don't see why the air handler could not be returned if it was never installed. The distributor may charge a handling fee for the return. It would be a small price to pay in order to get the right equipment and an installation which makes you happy.

If an HVAC sub-contractor will be doing the installation, I recommend you talk to him directly.