The only time you need an air to air heat exchanger is if you have a very tight house. This is unlikely in you case even with new windows. "High" humidity in the winter is not a bad thing since it will make the liiving space more comfortable. In the summer it can make the house uncomfortable. If you don't have central AC you might want you install a de-humidifier and use it for all but the summer months.
I suspect your house will be more comforatble this winter with the new windows and insulation.
i think my house is to tight because my 2nd floor gets to be around 90 degrees upstairs
That is simply a case of hot air rising. If you don't have insulation in your attic insulating and ventilating the attic will help some.
how can i tell if i need a air to air heat exchanger.
A house that has radiators has to be an older house. Only new construction is considered tight enough to warrant an air to air heat exchanger and this is primarily for indoor (fresh) air quality not controling the temp
how do i go about geting fresh air into my house other then opening up windows in the summer and how do i take care of my problem in the winter
Just open the windows in summer. An air to air exchanger is primarily for winter use in a residence.
thank you and can i talk to you by phone in more detail
A system with radiators (and only one zone/thermostat) is difficult to control in a multi level house. You could add a second zone for the second floor but that could be very expensive.
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One other thing you could try is balancing the system.
Do you have a steam or hot water system?
if i get a heat exchanger how do i know how many and what size
I don't think buying a heat exchanger will help your situaution. If you really want one you need to consult a local contractor for pricing and installtion.
thank you for your help
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