Finishing Basement - HVAC questions?
Question:I am finishing my basement and would like to tie into the existing HVAC system that heats/cools the whole house.
#1 - Is this a good idea?
#2 - Is this as simple as branching off the existing duct work for the supply and return and then adding the respective vents in the basement?
#3 - Do you know where I can find some more info on doing this?
Thanks for your help.
Answers:
1.) Yes its an excellent idea. One of the leading causes of moldy and damp basements is lack of circulating fresh air.
2.) Yes, just tap into the outbound vent and install a 5" or 6" Elbow and connect your 5" or 6" piping to it. Set your vents up so that the outbound is farthest away from the return duct so that you have across the room ventilation. If the room is very large you'll need two or more outbound vents. The return duct is very simple and can be a chamber in a wall farthest from the outbound vents and at the floor level.
3.) There are several DIY sites, just Google it.
When I finished my basement I wanted a full HVAC set up to keep the air fresh and ward off dampness and any possible mould. I tapped into the main outbound trunk (this was the hard part cutting into that darn thing at the top with little room to move the tools.). Then I installed an outlet Elbow which is square on one end and 5" or 6" round on the other end. Mount the square end by getting the tabs into the hole you cut and then reaching into the Elbow and turning the tabs up to lock the piece on. Secure with aluminum duct tape. Then I ran the pipe in sections to near the opposite end of the room from where my return was to be. At this point in the ceiling I installed a round register mount and after dry walling installed the adjustable round register. In my case the rear wall of the room ran up against the back side of the return trunk. All I needed to do was cut a square hole in between the studs and seal the area with caulk. When I dry walled, I caulked the two studs so the dry wall when applied made a sealed chamber with no insulation in it. On the inside of the room near the bottom I cut my hole where by braces were, and placed my return hole grille. Its been perfect at keeping fresh air circualting all year long when the system is running. Its cool in the summer and warm in the winter and most of all its nice and dry and fresh.
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I am building out my basement as well. I put in a small heat pump largely because it wasn't practical to try and pull duct work from above. If you have floor registers it might be different. Also, The efficiency of your current unit will help determine if you want to install a basement unit. I would consult an HVAC contractor in your area. They would be able to tell you what would be possible given your situation.
1).Sure it is if you like to save $. Just don't rob too much from your system. It will depend on how big your basement is.
2). If duct is rigid, purchase a " Y " branch that corresponds with the existing duct you plan to tap into. Flex duct is not recommended if dampness is an issue.Also I recommend putting dampers in the duct or you can purchase the damper already installed in the register cover. Try to put the vents above windows and openings to avoid cold patches.Point registers toward the center of the room.Duct tape and insulate all connections.Make sure return is larger than supply and at opposite sides of the room for proper air movement.Try to keep return close to the furnace.Don't bend the duct work over 90 degrees at any 1 point and insulate supply /return lines.You mite have to do a little fine tuning (by adjusting the existing dampers) to balance out the system.This should get you pretty well situated.
3).Lowe's,Home Depot, etc. provides a lot of do it yourself classes. Good luck.
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