If you try to put a 12 inch supply line off of that 10x6 trunkline, then yes you will have airflow issues. Look at it this way. Your 10x6 trunkline can handle around 260 CFM (cubic feet per minute), but that 12 inch pipe handles about 700 CFM. So, you could drop the size of that pipe you are running to an 8 inch piece of pipe and still keep your current static pressure. Do NOT go any bigger than that 8 inch pipe because you will lose a lot of pressure. It would be the difference of using a pressure washer with a good tip on it to clean your drive way or a hose with your thumb on the end of it trying to do the same job,

Well, the second guy was just out and I signed. Based on the layout of our basement he suggested on single duct run (to be done immediately) and 3 vents to be placed in the main duct. He actually reccomended adding them one a time once the cool weather returns thinking I may not need that many. I said I'd pay to have extra runs put in but he felt I'd be wasting my money and the vents in the main duct would suffice. He felt I may need a baseboard or two take the chill off if necesary. Remember, the basemnt is not a separate zone. He said I should box in the ducts and install the vents myself, that it was fairly simple. He suggested when my basement was complete, to have them back to install a return.

jb I have had a similar issue and finally fixed it. I have a 3 year old home that is well insulated and tightly sealed. It is a 2 story home with a basement with geothermal heat/cooling. The second story of the home contains only guest bedrooms that are rarely used. The second floor has its own dedicated hvac and I set the stats to cover extreme temps (set temp = 60 in winter, 82 in summer). These settings cover the rare extreme temperature cases but also enure that the hvac unit doesn't normally need to run to save on heating/cooling costs. It turns out that in the winter the warm air rising from the first floor actually keeps the rooms on the second floor warm enough that I don't normally need to run the hvac unit upstairs. However, not running the hvac upstairs is what caused the condensation problem like you have. The key to the issue is that the insulted ducts for the second floor rooms run throughout the attic. Even though the ducts are insulated and my attic is over insulated, the air and surfaces inside the ducts will get very cold if the hvac is left off. When the warm air rising from the first floor gets into the duct inlets a lot of condensation forms. But I notcied that the condensation only formed when the outside temps fell below about 20 degrees. The first time this happened, I soaked up the water on the carpet and then turned on the heat and everything dried up. I also noticed that as long as I ran the heat up there I did not get condensation even when the temps outside dropped to zero. I figured out that as long as I kept warm air moving through the ducts that the condensation would not form. But I did not want to run the hvac up there all winter because it is a waste of money. I had an idea that whenever the temps dropped below 25, I went upstairs and turned on the hvac fan but left the heat off. The idea was that continuously moving the warm air from the second floor rooms (which naturally get heat from the first floor) through the attic ducts would be enough to keep the inside of those ducts warm enough to not create the condition for condensation to form. This process proved to work for me but was a bit of a pain. I had to always remember to go up and turn the fan on at night and then shut the fan off in the morning. But it worked. AFter one season on manually turning the hvac fan upstairs on and off I decided to automate the system. Since I have a zoning up there, I checked the manual for my zone contoller (EWC Controls Ultra Zone 4) and found out that is has a dry contact input for a carbon monoxcide sensor. This feature allows the automatic detection of CO (with a seperate CO sensor) and allows the hvac fan and a freash air inlet to be automatically turned on to circulate fresh air through the system. I used that CO dry contact input to hook up a battery operated progammable timer with a dry contact closure so that every night at 6pm the hvac fan turns on, and every morning at 6am the fan turns off. I only turn this timer on during the months when nightime temps drop below 25 (generally Jan & Feb). This fixed my problem and saved me the hastle of doing it manually. When this problem first surfaced I thought about sealing up the registers upstairs but decided against that approach becuase there are times when I do run the hvac (when we have guests or when it is really cold outside) and so I would have to run up there and take the seals off. There are quite a few regsiters and it just wasn't a practical solution even though it probably would have worked. The challenge is making sure that the seals are air tight.

"The manufacturers of Vent Hoods are miseducating the consumers." Yes. Somewhat. Not really. They are in business to make money and they do that by making hoods as inexpensively as possible and then selling as many as they can for as much money as they can. Their goal is NOT your health or the IAQ of your home - that is up to you. Telling consumers that they'll also need to spend money on MUA if they buy hood X will negatively impact their sales (ignorant consumer will just go buy a hood from brand Y instead because it doesn't say you need MUA even though it has an identical need for MUA) so they do not want to do that. MUA is also not something that fits well within consumer hood manufacturers world except to the extent that they might offer a hood w/ integrated front curtain ducting. It is much more of a pure HVAC thing. It can be supplied to the return ducts of an HVAC system, the supply ducts or ducted directly to appropriate locations. Incoming air can be heated by gas, electric or hydronic. Incoming air may need to be humidified or dehumidified. It often needs to be electrically integrated with the HVAC system controllers to function properly. Consumer hood manufacturers - ARE NOT IAQ or HVAC people or engineers - they make something decorative that by nature must include air movement so they reluctantly include air movement in their product. Commercial hood manufacturers - ARE IAQ and HVAC people and engineers. Their customers are much more educated than consumers. The one singular purpose of the product they are selling is IAQ - so they design and sell systems that provide good IAQ. Aesthetics is quite secondary for them. Residential HVAC companies in the U.S. - ARE NOT IAQ people (they should be though). A tiny few, less than about 1%, know it well and a few more know it a very little but the vast majority know just enough, based on what they've been told at a 4 hr CEU course, to sound like they know what they're talking about but they don't really understand it. Most residential HVAC people do not understand air movement or why things are done the way they are - they only know how to use tables that tell them to do this or that and as soon as something is outside of defined parameters they're totally lost (though sometimes don't even realize that they're lost). Licensed Professional Engineers do (or most do, some don't) understand air movement and other elements. They are the people who create the tables that HVAC people use. They can think independently. Defined parameters for them are not tables but the physics of air - it's movement, temperature and components. Unfortunately, most U.S. engineers do not have a good understanding of human physiology (except perhaps for biomedical engineers). They do not, for instance, understand how CO2 functions in our bodies and how high levels of CO2 due to poor ventilation affect us. Or how poor ventilation resulting in high levels of VOC's, PM, Carcinogens and Pathogens affect us.