Air sealing and insulation are the two biggest things you can do to globally improve the efficiency of the home. 

There are several articles on this application and I have yet to be in a home that didn't need it. 

Tightening up the envelope across the attic surface will lessen air infiltration at all the other areas of the home. 

If you use a black light you can target the urine areas soak in white vinegar leave for ten min wet vacuum as much up as you can mix up a cup of water with a quarter size dawn dish detergant put in spray bottle saturate area but don't soak. Sprinkle baking soda around on the wet area spread likghtly. let sit until everything dries hard this could take up to a day. break up the crusted area with finger tips when dry then vacuum up. it is a bit time consuming but it is all natural and it works like  nothing else!

Verify that all window and door seals/weatherstriping is in good shape.

Check to be sure doors and windows are caulked properly (no gaps, cracks or missing).

If you have an attic access, treat it like door opening and seal properly. If possible, create an insulated cover to go over it in the attic.

Check HVAC ductwork for leaks and seal with foil tape or mastic.

Wrap your hot water heater in a blanket.

I would start with making sure your attic has adequate ventilation. 

Hello Alex, 

One alternative that most homeowners are not aware yet is reviewing your Roofing System. Along with the attic insulation, the type of roof you have can make a huge difference on how energy efficient your home is.

Most roofing materials (especially asphalt composite roofs) absorb solar energy and transfer heat to your home (requiring more air-conditioning during summer). On the other hand, energy efficient Metal Roofs are reflective and emissive. They bounce most of the sun's visible and UV light - meaning less heat transferred to your home. Independent studies show energy savings of up to 25%.

The Interlock Metal Roofing System is Energy Star certified (US only). More than energy efficient, our roofs are truly sustainable, being made of up to 95% recycled material, reducing the dependence of asphalt and stopping the cycle of old roofing material going to landfills. It is a lifelong solution that is better for your home, your pocket and the planet.

This time of year, we start receiving panicked emergency calls for leaky roofs that failed during the tough winter season. Most roofs fail long before their anticipated lifespan and not just because of their age.

Main reason? Improper attic insulation or ventilation prevents the continuous airflow of outside air into the attic. When ventilation is done right, there is a continuous airflow up through the soffits continuing through the ridge or mechanical vents. This helps during the warm summer months when attic temperatures can reach well over 130 degrees, as well as during the winter during that horrible “ice dam” building season.

The goal is to balance the airflow and temperature protecting the valuable living areas below. A good rule of thumb is one square foot of attic ventilation for every 300 s.f. of attic space. IE: If your attic is 1200 s.f., you’ll need a total of 4 s.f. of ventilation split equallywith 2 feet in the soffit/eave and 2 feet out the ridge or mechanical vents. This will ensure good airflow through the attic.

We all know of those dreaded ice dams ! Having the right amount of insulation keeps the heat where it should be, in your living area! When you do not have proper insulation, it allows the warm living space air below to rise making the attic warmer. The result is melting snow turns into water, water then runs toward the eave where it re-freezes creating ice dams. Water then builds up under the shingles and you know the rest of the story – wet ceilings, walls- a total mess.

We’ve seen all sorts of problems including mold, mildew growth, plywood deflection, curved shingles, wood rot, frame rot, etc.

Short term, the easiest way to keep your heating/cooling bills down and minimize your likelihood of an ice dam is to have proper insulation and attic ventilation. Long term, you’ll be extending the lifespan of your roof and preventing expensive repairs.