為房屋投保火災保險，保險金額與房屋 (包含屋內傢俱等) 的價值相等時，稱為「足額保險」，若保險金額低於房屋價值者，則稱為「不足額保險」。
理論上，若屬足額保險，則房屋因為火災造成的價值減損多少，保險公司均應全額負擔。但是，如果是「不足額保險」，依保險法第77條規定: 「保險人之負擔，以保險金額對於保險標的物之價值比例定之。」因此，民眾只能以投保金額與房屋價值的比例計算理賠金額。
舉例而言，如果房屋價值1000萬，但僅投保800萬之火險，今房屋因火災導致價值減損500萬，則因火險的保障範圍僅房屋價值的八成，故保險公司亦僅需理賠損失金額的八成，即400萬元。
If you buy fire insurance for your house, and the insured amount is equal to total value of the house (including furniture inside) , this is called full insurance. But if the insured amount is less than the value of the house, it is called underinsurance.
In theory, if your house is fully insured, then the insurance company should pay for all the damage caused by the fire. However, if the insurance is insufficient, then according to Article 77 of the Insurance Act: “the burden of the insurer is to be determined by the ratio of the insured amount to the value of the subject matter insured.”. So, the compensation is calculated proportionally – you get paid based on how much insurance you bought compared to how much the house is really worth.
For example: if your house is worth NT$10 million, but you only bought fire insurance for NT$8 million, and a fire causes NT$5 million in damages, the insurance will only cover 80% of the loss. This is because the insured amount is only 80% of the house’s value. So, the insurance company only needs to pay 80% of the NT$5 million loss, which is NT$4 million.