How do I keep my House warm in the Winter & Cool in the Summer

This is a common enough complaint and largely due to the insulation or rather lack of it in your house. Insulation is like putting on a coat in winter, it keeps the cold (or excessive heat) out. Houses are insulated in many ways but principally under the floor, in the external walls and in the attic or roof.
Many old houses were built before builders were aware of the need for underfloor insulation (not to be confused with underfloor heating). Generally to add this insulation to an old house would be very expensive. A high quality thermal underlay for a carpet or timber floor will certainly help and provide a cost effective solution. Talk to your supplier about the best underlay for this purpose.
Walls can be insulated in three ways; in the cavity, externally or internally. Pumping the cavity (if there is a cavity present) is the cheapest way to insulate and get a reasonable U-Value. Internally (dry-lining) is effective but very disruptive and often involves moving radiators and so on. Externally is by far the best but a very expensive process in itself.
An attic should have a minimum of 300mm of quilted insulation but many people now insulate to 400mm and beyond. Thus is a cost effective and highly effective solution and should certain,y be the first expenditure in any insulation project.
Beyond this good quality modern double glazed windows with vents compete the package. There are grants currently available from SEAI for all the above insulations and insulation is certainly one of the best investments you can make as though there is a high upfront cost, you stand to reap the benefits for many years, as long as it’s designed and installed correctly. Error on the side of having too much!