I also found an used/old three ports splitter (one input + two 3.5 dB outputs) from my goodies bag. I think I used this splitter before I got RadioShack's five ports splitter since I got more tuners. :P Its sticker label said:
RMS
DigiTap(TM)
Low Intermodulation Splitter
Model 1002DWSBSCTE
6KV Surge Protected
5-1,000 MHz
-120 dB RFI
CE
Made in China
I will try that too to see if it makes any differences in the other house's attic (just to try all rooms with TVs). Also, I found out that the attic's $25 splitter was from RadioShack. That's bad quality splitter, right?