I have an ICF home and am currently venting the dryer to the exterior. But with such an air tight home the dryer is causing a negative pressure in the house. So I am curious if anyone has a system where the heat is recaptured into the house in the winter and exhausted out in the summer via an air exchanger. 

 

Sounds like a HRV. Or, as was discussed elsewhere, use a condensing dryer or, if the dryer is electric, vent to the inside.

What does code in your area say you can do?

The dryer is a closed system. Simplest thing is to put another vent in from the outside and duct it to the drier intake. Keep it far enough from the dryer exhaust so that you're not sucking it back in.

Are you concerned about the effect of negative pressure, heat loss, or both? Whether gas-fired or electric, it's important to vent the dryer's moisture-laden exhaust air to the outside. Humidity builds up in the house fast enough without extra moisture from the dryer. I, too, have a tightly built house. Negative pressure buildup will reduce the air flow through the dryer, reducing it's efficiency. A long exhaust duct further impedes air flow through the dryer, so it's important to keep the duct as short and as straight as possible. Unfortunately, most dryers don't have an intake pipe to create a closed system. You can always open a window a crack when running the dryer to relieve back pressure. if necessary. I assume you have an HRV for ventilation. Any negative pressure differential induced by the dryer will be limited by an increased volume of fresh air entering through the HRV. Some negative pressure is tolerable as long as other fuel burning appliances (furnace, water heater, fireplace) are closed systems.

As to dryer heat recovery, there are condensing dryers as mentioned already. Europeans use them where an external vent is unavailable. Everything I've read about them indicates that they are better avoided.