HVAC and insulation questions

[Frank W]

I'm close to being ready for insulation and HVAC.
I'm building the 20X34 2.5 story cottage so the attic is just 2x8's and knee walls. The third floor/loft will be 2 bedrooms. I was think about having that part sprayed/expanding to keep the loft cool in the summer. Thoughts on insulation?
My other question is HVAC. Here in the south it gets to single digits in the winter and triple digits in the summer. Huimity is high. From what I understand a heat pump don't work well in this wide range of temps.
I will have a wood stove for winter heat but I still want the option of heating with electricity.
I have read central heat and air condition loose out from the ducts and the way the house is built I'm concerned about cutting the LVL beams for duct work.
I have thought about mini splits. Could you guys give me your thoughts on these issues?
Thanks!

[John Raabe]

Up in Western WA I have a mini-split and wood stove combination. The initial system was a forced air electric furnace but that was too expensive to run. The mini-split is simple and runs cheaper than buying the wood we used in the stove. However, you have a larger and taller house so you may need units on each floor. You also have a much larger cooling load.

These insulation and heating/cooling strategies are very local and climate specific.

[flyingvan]

With those large temperature swings, sounds like a great application for a ground source heat pump.  Someone I work with installs them.  If we had the cooling issues I would have gone that route but our summers are pretty mild and there's always plenty of oak to burn in winter
http://www.igshpa.okstate.edu/geothermal/

[rick91351]

If you have a good water source (cheap and plentiful) water to air heat pumps work well.  Air to air work well but needs an electric back up when it gets cold cold.  However I really don't think it is a DIY project.  I know ours was sure not.  And ours was one level and had to be inspected by the state and be in compliance with the Federal Energy requirement.  We had to pay for a engineering study and that determined the size and and placement of ducting and size of unit.  Air returns are in the ceiling and has floor registers.  It was nothing like going down and getting some sheet metal ducts and going to work.  In fact none of the ducting were anything like that. 



Same way with our insulation with the Federal Energy requirements and inspections that was money so well spent.  We hired the most reputable company around and my word they did so much more than I / we would have or more importantly knew to do.  I would sure consult with a couple insulation contractors even if I were going to DIY.   

       

[Frank W]

Thanks for the replays.
I ordered a Mitsubishi multi split system. One 36,000 btu outside unit and a 12,000 btu inside unit on each floor. It draws 3000 watts heating and 3700 watts cooling. I should have it installed in a few weeks