The 800 I believe will run even if HVAC is not running. It will humidify a lot more space.

I have an aprilaire power humidifier (like the 700, but not sure what model as it was installed 10 years ago) and it works great EXCEPT we get white dust all over the area around the furnace.

It's really irritating, not sure if it's because we use soft water, or if the unit is back-blowing deposits out when the unit fan is off but furnace is on, but just for this reason if the 800 doesn't have a fan it might be worth it in my experience.

How large is your house and what is your location? Why do you think you need a humidifier?

Many houses are dry in the winter because of air infiltration through windows and doors. A new house should be tight and may not need a humidifier. In general humidifiers are a maintenance problem and should be avoided if possible. Think this over carefully.

I don't own a humidifier, but I have been told if you have to get one the steam type is the best.

He is right that if your home is very well sealed too much humidity rather than too little can be a problem. However, if you put in a humidifier that has a humidistat it won't run unless needed and our last home (about 5000 sq ft) that was entirely spray foamed and had an ERV had an aprilaire unit that ran quite frequently in the winter so at least my experience is that a humidifier is still a good idea. It's even more important with a hardwood home (which our entire home was) because of the wood fluctuations with humidity.

As a general rule general contractors know very little when it comes to HVAC and they hire the low cost HVAC contractor. The contractor will want to install a budget HVAC system and then want a lot of money to upgrade it to better equipment.

If the house is being built on a slab, then getting the humidifier is a good idea. If the house will have a full basement, then you probably don't need it. You will be get a good amount of moisture coming up from the basement through the hard wood floors. If you want piece of mind then get it. It can always be turned off if it is not needed.

PPrioroh, that helps out, thanks. It sounds like it's a good idea, but I'm still not clear how you know you need one before the house is built. Looks like I need to ask more questions because on the Aprilaire website it says the 800 is "This steam humidifier is designed for applications such as crawlspaces, attics, areas of the country with milder winters with non forced air heating. " And he's proposing to pair with the Carrier single stage, constant speed natural gas fired furnace.

Mike_Home, would it be a lot more difficult/expensive to add it on later if we need it? What else,if anything, would it impact now?

It should not be difficult to add it later. A little planning will make the future installation easier. You want to install a thermostat now that can control it in the future and has the extra wire in place. That should not be a big expense.

It may cost a little more on labor, but then again the prices quote to the 800 seemed high. It may turn out the cost would be the same if you did it later.

Thanks, Mike, I'll look into it!