[gegamun]

Concerning forced air furnace system: I need to know how to design HVAC runs to get through a foundation wall that holds a suspended slab to reach living space under a garage. A further complication is that there is a 2 foot step down into that living space. I need to know both ceiling runs and under ground solutions. Is one of these easier than the other?

[talaniman]

A layout drawing would help a lot... with dimensions. Do you have an existing system in place? If so please describe it.

Without a total number of square feet to be utilized, calculations/costs/and project scope cannot be accurate.

[gegamun]

[talaniman]

Thank you for the drawing. Do you have a existing system to describe? What is your general regional location?

[gegamun]

Thank you for the drawing. Do you have a existing system to describe? What is your general regional location?

No. This is new construction not yet started. Mountain West region.

[talaniman]

To be clear you have no existing furnace or duct work? That would be incredible.

However I can recommend this site to give you ideas to guide your project.

http://www.perfect-home-hvac-design.com/

Are you doing this yourself, or will hire contractors? Contractors will be as constrained by local codes as you will be. But for costs issues and building practices you cannot beat their input.

[gegamun]

A contractor will be doing the work. I was trying to find out if there would need to be a block out in the wall for duct work to be fed through, how large it may need to be to fit both supply and return runs. If they should be next to each other or separated, etc. A HVAC contractor will be doing work, I am just planning for it.

[talaniman]

These sites may be very helpful to your planning,

Cost to Install Duct - 2015 Cost Calculator (ZipCode based)

Cost of Ductwork - Estimates and Prices Paid - CostHelper.com

Furnace Ductwork Installation Costs-- for Goldenseal Construction Estimating Software

Use all 3 to get a more reasonable high/low and average. They all include some very good articles and links and the first one has a good link specific for whatever your location is. I figure you have just under 1900 square feet with some special needs area, and doubt underground ducting is a viable option but you never know.

Central air and heating is the way to go for my money, long term. I live in the southwest though. Texas to be specific, and you gotta have AIR conditioning!!!

Average unit cost are 5-$7500 bucks without ductwork, depending on size and area of application needs.

[gegamun]

Thanks for your time. I will check out the sites.