Great Idea


Hopefully you did read my blog Basement Finishing 101 and now know how valuable this first step making a perfect plan is in the entire construction process of basement finishing. So first let’s take a walk around the basement and you might want a step ladder and flash light handy.  If your basement has a forced air furnace and you have a main supply line, look at all the sheet metal connections and if they are not sealed up as you see in the following image, you may want to take care of these leaking spots first;

Sealed Air Duct
Sealed Air Duct

If it’s not sealed like this, make note that forced air furnaces build up a low amount of air pressure also known as static pressure. I’m not an HVAC expert but common sense will indicate that what goes in must come out. In two story homes requiring heat or more so air conditioning to the 2nd floor, almost always have an issue cooling the 2nd floor and not as much of an issue with heat since heat rises and cold air falls. So before any walls are built in the basement, you want to make sure your system is fully efficient since you won’t have a chance to remedy this thereafter.

Here’s some simple math you can do and this is provided your furnace has enough BTU’s (British Thermo Units) for output per hour to not only heat the other floors of the home but the basement as well. If not, there are options before you go and replace the furnace or add a 2nd furnace. Note that in replacing an older furnace that is only 80% efficient with a HR (high recovery) unit which is also wise in that it can slowly pay for itself over time as well.  This is provided that the existing unit has had a good life with enough payback because if not, the old unit can be sold on Craigslist or maybe eBay to help with the cost of the newer unit. There are a few ways to calculate BTU’s depending on the type of heating system you have and the type of fuel that is being burned not to mention other factors such as windows, temperature needs and so on. I suggest using a web site calculator such as the one found at this link;  BTU Calculator and this following link explains all this much more; How to Calculate BTU Per Square Foot In my opinion and using this basement finishing 102 knowledge, if the BTU’s are enough for cooling then it’s more than adequate for heating since conditioned air blows slower than heated air in most systems.

If you have all your square footage, here’s a quick reference chart below:


I believe the above chart is based on an average 8 foot high ceiling and vaulted or higher ceilngs is another formula. If you don’t meet up to your demands in BTU’s there are other ways to achieve your goals. I call these other methods as supplemental heating if needing to get the basement heated well without spending big bucks. Go to this link to read all about Basement Supplemental Heating by John Browning.

So now that you have some informal education on BTU’s and determining your heating and cooling needs, just make note that most basements DO NOT require cooling (air conditioning) and totally depending on your local climate.


Better air flow to the 2nd floor (Basement Finishing 102 continued)

Let’s go back to the issue of getting the  cooling to a 2nd floor and or other parts of the house that seem inadequate and again, you want to get this done before you finish the basement space. First measure all your output ducts/vents also known as registers. Length times width of the duct opening in other words. You’ll get square inches and multiply this times the number of vent openings you have unless if different in width and length. The objective is to find the total square footage converting the square inches by 144 or merely using this online converter. Don’t include the cold air return or air input vent but do have the square inches of this separate and handy. Then compare your total square inches of the registers or air output vents with the total of the cold air vent. Is it the same? Remember what I mentioned above; “what goes in, must come out” and factoring in distance of air duct runs (air travel) and the size of duct going from the furnace to the 2nd floor too. It’s possible the HVAC installer undersized these as well. If the cold air return vent is undersized in square inches to the total of all air output vents or registers, this is your issue of not getting enough cold air to the 2nd floor or other areas.

One easier way to add an additional cold air return is using round insulated flexible duct. These come in different sizes yet round and other factors play a role in this too such as friction loss inside the ductwork.  The following link should satisfy even the most complex questions; Equivalent Diameter Chart

So for example, say you need to add 140 square inches to an area of the home or 2nd floor, you’d want to install a 10X14 inch cold air return using a 12″ round flexible insulated duct. Ok, you’re wondering now where to run this and how to get it to the 2nd floor, right? For some, installing a 2nd cooling unit in the attic works the best but the idea that the cold conditioned air should blow down from the highest point as possible is the objective in this. So unless you build a chase through parts of existing closets and such going up to the 2nd floor, the other way is using your attached garage space. You should be able to find a route high in the basement ceiling along the garage foundation to cut through and easily go up into the attic of the garage to reach some portions of the 2nd floor. Again, I’m merely suggesting ideas and methods in this basement finishing 102 blog and by inviting HVAC guys out to pick their brains is normally free. And you might ask for their price to make this impovement as well. Other methods to get additional ductwork installed? Framing with a matching exterior finish can add a chimney looking chase on the outside of the house to also accomplish this. Additionally, sometimes it’s just best to add a separate air conditioning system in the attic with the ductwork blowing down. This makes a separate zone as well that can run independently saving money working more efficiently.

Inspecting your existing ducts

As you saw in the first photo above of a properly sealed duct on the main trunk line from the furnace, you should make sure also that any joints or connection in any duct work including all round ducts have duct tape or better yet, this duct sealant which can be bought at places like Home Depot or Lowes. It’s a messy job but needs to be done. A ladder may be needed to see all of it well.

Note the issues found in the following image;

Duct Leak

Still can’t see it? Well, let’s zoom in and see this image larger below;

Duct Leak Zoom

Here’s how  you can see this issue better in the image below with arrows and notes;

Duct Leak Zoom Notes

Surprised? Well yes, these openings are all allowing your cold air return to pull air in from the basement space back to the furnace thus preventing your cold air returns on the floor or floors above to not pull air efficiently and this also means that the air flow coming out your vents is less than it could be. These too need to be sealed up and if larger ones, use silicon caulk, liquid foam or some type of thicker caulk that sets fast. Now you’ll know why I wrote basement finishing 102; If one was to calculate all the openings found in a basement duct work system, I’m sure it would add up to be a substantially large opening suck air from the basement and not flowing efficiently where it’s needed.

Here’s another area to inspect seen in the image below;

Duct Leak 2

Still can’t see it? Well, let’s zoom in and see this image larger below;

Duct Leak 2 zoom

Here’s how  you can see this issue better in the image below with arrows and notes;

Duct Leak 2 zoom notes

The following image is a good example of filling gaps using a can of urethane foam to seal all gaps. This is also used to fill holes between floors as a fire stop.


I hope you appreciate this information in my basement finishing 102 even though this was almost another novel of mine but all this should pay off if you first seal off all openings and connections in any of the sheet metal and or duct work found in your basement before you build any walls, soffits or ceilings. Don’t forget to check all round ductwork! Too many basements get finished without this issue being resolved and guess what? That’s right, the following years will be of a system running at less than efficient levels also wasting money endlessly thereafter. Even if you’re not finishing the basement any time soon, your system will run at its best efficiency if you follow these steps thus saving you money that you can send to me, ha, ha.

Don’t miss reading my blog Basement Finishing 101 if you still don’t have a design and look for Basement Finishing 103 coming up regarding other preparation needed before you build. Thank you and please contact me no matter what your question might be.

I also recommend many products for construction, just ask me but new and or replacement windows and exterior glass doors being used in Colorado or anywhere at high altitudes must be manufacture at the same altitudes. Why? Argon gas filled windows made at lower altitudes come shipped with breather tubes and you’ll lose the Argon gas (efficiency) as it ships to a higher altitude. Just use my link Contact Me and I’ll put you in touch. If in Colorado, you’ll get wholesale pricing.