I have a single level home with big open attic it has blown insulation and very narrow crawl space but my furnace electric has the single return air duct running about 4 feet from furnace it is in lowered ceiling from bathroom to kitchen ,, my question is can I use a flexible hvac pipe duct an d run a network to living room and two bedrooms the way it is now is very in sufficient, furnace runs almost constantly in cold months , I would appreciate your professional opinion and tips what to do thanks.
Hi, Bill, Great question! I live on a 3rd floor condo with forced air heating. I have accordion style vents in the attic. Would insulating them help the situation? Furnace and ac units are brand new and appropriate for the unit size.
Hi, Kenneth, Great question! He will contact you soon to discuss featuring it during an upcoming show. Take care! A part of me has to wonder how the cost-benefit breaks down when buying pre-insulated piping. Save my name, email, and website in this browser for the next time I comment. Today's Homeowner. Expert Advice on Improving Your Home.
Your heating, ventilation and air conditioning system needs insulation for optimal performance. When working with fiberglass insulation , always wear: Goggles Protective clothing Approved dust mask Gloves are a good idea, too, but it can be hard to do the delicate fitting and taping required while wearing them. Repair a hole in HVAC ductwork using foil tape followed by duct mastic. Please enter your comment! Please enter your name here. You have entered an incorrect email address! Stay Tuned. The ducts are exposed to the same cold, heat and humidity that exist on the outside.
Insulating them is essential in colder climates, optional in milder ones and necessary in humid climates to prevent condensation. In all cases, the ducts need airtight seals at all joints, seams and takeoff points before the insulation is applied. If the ducts are inside the house but in a basement ceiling or between the first and second floors of a two-story house, condensation can form and leave water stains on the ceilings below.
If the ducts are accessible, insulate them to prevent condensation. Before applying insulation, make sure the ducts are not already insulated on the interior. Ok, I've got old uninsulated ducts. What should I do? Assuming you're keen to fix this problem, you have two options: Insulate your ducts Replace your ducts with insulated ducts The choice is yours, and you're going to be better off no matter which option you choose.
Insulating your ducts Adding insulation to your ducts isn't as simple as getting some duct wrap and taping it together. Wrap fiberglass duct insulation around the ducts and tape the seams together. Of course, you might also consider… Replacing your old ducts Out with the old, in with the new!
But whether you hire us or somebody else, be sure your contractor follows these steps: Perform a Manual J load calculation: This is the step we and others take to determine the right size for your HVAC system. Why do it before getting new ducts? Because if you the size of the system affects the size of the ducts. Perform calculations for Manuals S, T, and D: These exercises help us select the right HVAC components, determine air register and grille sizes, and determine the correct length and positioning of the duct runs.
Install insulated hard pipe ducts: Flexible ducts aka flex ducts are usually best avoided. They're ok for very short duct runs, but longer flex duct runs have a tendency to sag and restrict airflow over time. It's not impossible to have an all-flex system, but extremely special care must be taken to install flex ducts properly. For these reasons, we almost always prefer hard pipe ducts. Test for leaks and balance airflow: In addition to sealing leaks see the process described above , we use a digital hood to measure the airflow in each room according to that room's need for air.
Then we balance the airflow to make sure there's enough air moving to every room. So, which is it? That is what I was hoping. I appreciate your quick response. Can you give me your opinion on this insulation job? JC, I think the duct insulation may be the least of the problems in that townhouse. The air flow is probably pretty bad and once the sheetrock goes up, those ducts are there for decades.
Thanks for taking a look. Seeing that type of work is a constant disappointment but I put much of the blame on the developer. This scenario can be avoided in design i. That said, every metal supply-side component should be insulated if system is located in an encapsulated attic or crawl. I meant to mention the risk of condensation but I think that slipped my mind before I finished, so thanks for bringing that up.
I did discuss the issue of condensation on uninsulated intake ducts for ventilation systems in my article on cold weather ventilation problems last month. I believe our Florida code I believe our Florida code required insulation for ductwork within conditioned space is R4. Curt, good for Florida for Curt, good for Florida for requiring insulation! I recall a conversation with a building code official in North Carolina probably 10 years ago.
He acknowledged neither the I-code or NC code address this issue, but their inspectors are supposed to make it clear to HVAC contractors that if their ducts sweat, they own it. BTW, I think R4 is more than adequate, even in severe conditions.
Assuming worst-case temperature gradients, the surface temperature should remain within 5F of ambient. Or perhaps if two flex ducts were mashed tight together. There are multiple requirements for insulation when it is used, but only that one for when insulation is actually required.
There is another issue that has been slow coming to the surface. That is the surface area of the ducts. The other way is to minimize the area of the ducts. Than means smaller AC, furnace of Heat Pump, centrally located air handler and short ducts to the inside wall of each conditioned room. Certainly no longer than to the center of the room.
One additional advantage is shorter ducts present less resistance to air flow. One of my biggest problems with Manual D is that it ignores the surface area and just calculates sizes for the stupid design you give it. I agree with John, and will I agree with John, and will add one more option to reduce duct area. Instead of putting in one large system, put in two smaller ones. Not only will this allow shorter and smaller ducts, but it will give better zone control.
Manufacturers tend to optimize their designs for equipment in the 3-ton range. The largest systems 5-ton are far from optimal because of size constraints in the field. So there are other advantages to using two 2. Yes, it will probably cost more, but you get what you pay for. Thank you for pointing that out. What are you thoughts on encapsulating ducts wrapped in R8 in an unconditioned attic with spray foam as shown in this US Department of Energy link?
Is this something worth doing as a DIY in lieu burying the ducts in insulation? Current my ducts are suspended about 2 feet above the current blown in insulation, and I am in the Pacific Northwest zone 4 in the Marine Zone. Adam, I like the idea of buried encapsulated ducts or even just ducts encapsulated with closed-cell spray foam.
Until recently I thought it would be a great way to go. That problem is noise. What this person told me is that the thermal expansion and contraction of metal ducts encapsulated in closed cell spray foam creates a banging noise when the system comes on after having been off for a while. Thanks, I was considering the Thanks, I was considering the use of closed-cell foam for a poorly ventilated very hot attic in Eastern Tennessee after reading the problems of condensation.
My guess: advantages are that closed cell should not allow condensation to be trapped within it and it has an excellent R-value per inch. The Disadvantage is that this can get expensive for large areas of duct surface. Another advantage is that, depending on access to the space and spraying skills, this can be much easier to install. Obviously you must be able to get a foam tank or long hose within range of the application. The foam I am familiar with is a two-part that mixes at the nozzle and that starts the foaming reaction as it sprays out.
Another advantage is a high R-value per weight. Foam has a higher R-v than fiberglass due to the closed-cell structure. And that makes it better at resisting condensation. After all, foam is used in marine, subfloor basement areas, etc. In my opinion, the presentation at the DoE link you posted seems to have lost sight of the rationale for using closed cell foam on attic ducts! Closed-cell foam is very expensive, especially the first lift 1.
In fact, the building code now describes how that may be done. In a vented attic, this can happen when the duct is in close proximity to conditioned space i.
In this case, the temperature gradient between supply air and the ceiling can be such that the duct surface could be cooler than the local dew point. You can accomplish the exact same thing with conventional air sealing plus an additional layer of fibrous insulation with a vapor barrier.
But even then, some manner of cost analysis should be done. From a cost-benefit and IAQ standpoint, the highest priority is getting the return side tight including the negative side of the AHU cabinet.
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