We looked into using the house system, but where the room is positioned on the house and where the existing trunks are would make it difficult and costly to new duct work...especially the returns. My wife and I are wondering if we can live without the AC...there may be a some days we can't use the room due to the heat. But do I go to the cost of the remodel and then be uncomfortable in July and August?

Old-fashioned swamp coolers only work in very dry climates and you need a route for regress of the cool, humidified air to the outside. Under some conditions, any air from the swamp cooler mixes with the mechanically-chilled air, you existing AC will get slapped with the huge load of removing the added humidity. Maybe you are talking about some new-fangled type with a heat exchanger instead? By "portable unit" do you mean the ones with wheels and hoses? Any of those will be less efficient than a conventional window unit so I suggest you go with a window unit. If you have to go with a movable, portable unit, be sure to get one with two hoses rather than one. Single-hose models are very inefficient. O.K., Willard, how many rats do you have? Be nice to those rats. Since they are captive, you have a great responsibility to keep Ben and Socrates comfortable. Seriously, rats, among rodents, make the best pets, but they are the smartest and need to be kept entertained to say mentally healthy. They are not easily amused. Give them lots of toys in the cages and keep them cool. For cooling you could experiment with giving them some of those freezer packs in the cages. Just tossing them in there probably won't work because direct contact will be too cold and uncomfortable. One option would be to insulate the packs on five sides and semi-insulate the top so they can lie on a cool surface. Another thing to try would be to build them a small, insulated box with an entry hole. Divide the interior to wall-off the freezer pack. Experiment and see what they like better. If you are going to rely on this, make sure that you don't forget before leaving and make the poor little fellows suffer. You obviously can't leave for more than a few hours or maybe a day which is a serious drawback.

Did the builder size the HVAC unit currently servicing the main level so that it could accomodate the basement? if so, adding the duct work for the basement is not a big deal. Post some details on what size units you currently have for each level and the sq footage. In my first home, they did no duct work in the basement but they did size the heater and AC unit to accomodate the basement living space. I acted as my own general contractor when I finished the beasment and I paid an HVAC company $1200 (this was in 1998) to add in ducts & registers in the basement. I did not add a seperate zone down there but could have easily done it for not much more. The basement was mostly below grade and worked fine running off the tstat on the main level. One thing you should get right now is a humidistat (costs about $20) and measure the humidity in your basement. With tighly sealed and insulated houses, moisture can be a big issue in the basement and lead to musty smells or mould. You might find that a dehumidifier is a worthwile investment when you finish your basemenent. I just added a large dehumidifier made by Sante Fe in my basement (currently mostly unfisished with some HVAC ducts) and it not only controls the humidity in the the basement, but we get the effects of drier air on the main level as well. This fixed a musty smell that my wife detected soon after we moved in, and then mildew spots we found on the basement cement floor when we had temperatures that were in the low 70's but humidity around 80% - very damp. Best of luck.

The answer here is the obvious one: You need to insulate and install storm windows. Do that before you consider any equipment - otherwise it will all be sized incorrectly. There are ways to insulate the house. Cellulose can be blown in from the inside or the outside. Closed Cell Foam can also be injected the same way. Cellulose can be blown into the attic and the crawl space walls/rim joists can be sprayed with foam also.